This file is intended to present some technology topics that cannot be assigned to a particular mission. The following chapters contain only short descriptions, they are presented in reverse order. The topics should be of interest to the reader community.

05 August 2019: An international
team headed up by Alexander Holleitner and Jonathan Finley, physicists
at the Technical University of Munich (TUM), has succeeded in placing
light sources in atomically thin material layers with an accuracy of
just a few nanometers. The new method allows for a multitude of
applications in quantum technologies, from quantum sensors and
transistors in smartphones through to new encryption technologies for
data transmission. 1)2)

Previous circuits on chips rely on
electrons as the information carriers. In the future, photons which
transmit information at the speed of light will be able to take on this
task in optical circuits. Quantum light sources, which are then
connected with quantum fiber optic cables and detectors are needed as
basic building blocks for such new chips.

Figure 1: By bombarding thin
molybdenum sulfide layers with helium ions, physicists at TUM succeeded
in placing light sources in atomically thin material layers with an
accuracy of just a few nanometers. The new method allows for a
multitude of applications in quantum technologies (image credit: TUM)

First step towards optical quantum computers:
"This constitutes a first key step towards optical quantum computers,"
says Julian Klein, lead author of the study. "Because for future
applications the light sources must be coupled with photon circuits,
waveguides for example, in order to make light-based quantum
calculations possible."

The
critical point here is the exact and precisely controllable placement
of the light sources. It is possible to create quantum light sources in
conventional three-dimensional materials such as diamond or silicon,
but they cannot be precisely placed in these materials.

Deterministic defects: The physicists then used a layer of the semiconductor molybdenum disulfide (MoS2)
as the starting material, just three atoms thick. They irradiated this
with a helium ion beam which they focused on a surface area of less
than one nanometer.

In order to generate optically
active defects, the desired quantum light sources, molybdenum or sulfur
atoms are precisely hammered out of the layer. The imperfections are
traps for so-called excitons, electron-hole pairs, which then emit the
desired photons.

Technically, the new helium ion
microscope at the Walter Schottky Institute's Center for Nanotechnology
and Nanomaterials, which can be used to irradiate such material with an
unparalleled lateral resolution, was of central importance for this.

On the road to new light sources:
Together with theorists at TUM, the Max Planck Society, and the
University of Bremen, the team developed a model which also describes
the energy states observed at the imperfections in theory.

In the future, the researchers also
want to create more complex light source patterns, in lateral
two-dimensional lattice structures for example, in order to thus also
research multi-exciton phenomena or exotic material properties.

This is the experimental gateway to
a world which has long only been described in theory within the context
of the so-called Bose-Hubbard model which seeks to account for complex
processes in solids.

Quantum sensors, transistors and secure encryption:
And there may be progress not only in theory, but also with regard to
possible technological developments. Since the light sources always
have the same underlying defect in the material, they are theoretically
indistinguishable. This allows for applications which are based on the
quantum-mechanical principle of entanglement.

"It is possible to integrate our
quantum light sources very elegantly into photon circuits," says Klein.
"Owing to the high sensitivity, for example, it is possible to build
quantum sensors for smartphones and develop extremely secure encryption
technologies for data transmission."

Driverless shuttle

10 July 2019: ESA’s technical heart will be serving as a testbed for this driverless shuttle in the coming months. 3)

The Agency’s ESTEC
establishment in Noordwijk, the Netherlands, is working with vehicle
owner Dutch Automated Mobility, provincial and municipal governments
and the bus company Arriva to assess its viability as a ‘last
mile’ solution for public transport.

The fully autonomous vehicle
calculates its position using a fusion of satellite navigation, lidar
‘laser radar’, visible cameras and motion sensors. Once it
enters service in October it will be used to transport employees from
one side of the ESTEC complex to the other.

The fully-electric, zero-emission
shuttle will respect the on-site speed limit of 15 km/h, and for its
first six months of service will carry a steward to observe its
operation along its preprogrammed 10-minute-long roundtrip.

Figure 2: This driverless shuttle will soon be tested at ESA/ESTEC in the Netherlands (image credit: ESA, B. Smith)

New Method Can Spot Failing Infrastructure from Space

09 July 2019: We rely on bridges to
connect us to other places, and we trust that they're safe. While many
governments invest heavily in inspection and maintenance programs, the
number of bridges that are coming to the end of their design lives or
that have significant structural damage can outpace the resources
available to repair them. But infrastructure managers may soon have a
new way to identify the structures most at risk of failure. 4)

Figure 3: A satellite view of the
Morandi Bridge in Genoa, Italy, prior to its August 2018 collapse. The
numbers identify key bridge components. Numbers 4 through 8 correspond
to the bridge's V-shaped piers (from West to East). Numbers 9 through
11 correspond to three independent balance systems on the bridge. In
the annotated version, the black arrows identify areas of change based
on data from the Cosmo-SkyMed satellite constellation (image credit:
NASA/JPL-Caltech/Google)

Scientists, led by Pietro Milillo of
NASA's Jet Propulsion Laboratory in Pasadena, California, have
developed a new technique for analyzing satellite data that can reveal
subtle structural changes that may indicate a bridge is deteriorating -
changes so subtle that they are not visible to the naked eye.

In August
2018, the Morandi Bridge, near Genoa, Italy, collapsed, killing dozens
of people. A team of scientists from NASA, the University of Bath in
England and the Italian Space Agency used synthetic aperture radar
(SAR) measurements from several different satellites and reference
points to map relative displacement - or structural changes to the
bridge - from 2003 to the time of its collapse. Using a new process,
they were able to detect millimeter-size changes to the bridge over
time that would not have been detected by the standard processing
approaches applied to spaceborne synthetic aperture radar observations.

They found that the deck next to the
bridge's collapsed pier showed subtle signs of change as early as 2015;
they also noted that several parts of the bridge showed a more
significant increase in structural changes between March 2017 and
August 2018 - a hidden indication that at least part of the bridge may
have become structurally unsound.

"This is about developing a new
technique that can assist in the characterization of the health of
bridges and other infrastructure," Millilo said. "We couldn't have
forecasted this particular collapse because standard assessment
techniques available at the time couldn't detect what we can see now.
But going forward, this technique, combined with techniques already in
use, has the potential to do a lot of good."

The technique is limited to areas
that have consistent synthetic aperture radar-equipped satellite
coverage. In early 2022, NASA and the Indian Space Research
Organization (ISRO) plan to launch the NASA-ISRO Synthetic Aperture Radar (NISAR),
which will greatly expand that coverage. Designed to enable scientists
to observe and measure global environmental changes and hazards, NISAR
will collect imagery that will enable engineers and scientists to
investigate the stability of structures like bridges nearly anywhere in
the world about every week.

"We can't solve the entire problem
of structural safety, but we can add a new tool to the standard
procedures to better support maintenance considerations," said Milillo.

The majority of the SAR data for
this study was acquired by the Italian Space Agency's COSMO-Skymed
constellation and the European Space Agency's (ESA's) Sentinel-1a and
-1b satellites. The research team also used historical data sets from
ESA's Envisat satellite. The study was recently published in the
journal Remote Sensing. 5)

Atomic motion captured in 4-D for the first time

27 June 2019: Everyday transitions
from one state of matter to another—such as freezing, melting or
evaporation—start with a process called "nucleation," in which
tiny clusters of atoms or molecules (called "nuclei") begin to
coalesce. Nucleation plays a critical role in circumstances as diverse
as the formation of clouds and the onset of neurodegenerative disease. 6)

A UCLA-led team has gained a
never-before-seen view of nucleation—capturing how the atoms
rearrange at 4-D atomic resolution (that is, in three dimensions of
space and across time). The findings, published in the journal Nature,
differ from predictions based on the classical theory of nucleation
that has long appeared in textbooks. 7)

"This is truly a groundbreaking
experiment—we not only locate and identify individual atoms with
high precision, but also monitor their motion in 4-D for the first
time," said senior author Jianwei "John" Miao, a UCLA professor of
physics and astronomy, who is the deputy director of the STROBE
National Science Foundation Science and Technology Center and a member
of the California NanoSystems Institute at UCLA.

Research by the team, which includes
collaborators from Lawrence Berkeley National Laboratory, University of
Colorado at Boulder, University of Buffalo and the University of
Nevada, Reno, builds upon a powerful imaging technique previously
developed by Miao's research group. That method, called "atomic
electron tomography," uses a state-of-the-art electron microscope
located at Berkeley Lab's Molecular Foundry, which images a sample
using electrons. The sample is rotated, and in much the same way a CAT
scan generates a three-dimensional X-ray of the human body, atomic
electron tomography creates stunning 3D images of atoms within a
material.

Miao and his colleagues examined an
iron-platinum alloy formed into nanoparticles so small that it takes
more than 10,000 laid side by side to span the width of a human hair.
To investigate nucleation, the scientists heated the nanoparticles to
520 º Celsius ( 968º Fahrenheit), and took images after 9
minutes, 16 minutes and 26 minutes. At that temperature, the alloy
undergoes a transition between two different solid phases.

Figure 4: The image shows 4D
atomic motion is captured in an iron-platinum nanoparticle at three
different annealing times. The experimental observations are
inconsistent with classical nucleation theory, showing the need of a
model beyond

SUN-to-LIQUID (Fuels from concentrated sunlight)

June 2019: The EU (European Union)
energy roadmap for 2050 aims at a 75% share of renewables in the gross
energy consumption. Achieving this target requires a significant share
of alternative transportation fuels, including a 40% target share of
low carbon fuels in aviation. 8) Therefore the European Commission calls for the development of sustainable fuels from non-biomass non-fossil sources.

In contrast to biofuels, solar
energy is undisputedly scalable to any future demand and is already
utilized at large scale to produce heat and electricity. Solar energy
may also be used to produce hydrogen, but the transportation sector
cannot easily replace hydrocarbon fuels, with aviation being the most
notable example. Due to long design and service times of aircraft the
aviation sector will critically depend on the availability of liquid
hydrocarbons for decades to come . 9) Heavy duty trucks, maritime and road transportation are also expected to rely strongly on liquid hydrocarbon fuels. 10)
Thus, the large volume availability of ‘drop-in’ capable
renewable fuels is of great importance for decarbonizing the transport
sector.

This challenge is addressed by the four year solar fuels project SUN-to-LIQUID kicked off in January 2016.

The European H2020 project aims at
developing a solar thermochemical technology as a highly promising fuel
path at large scale and competitive costs.

Solar radiation is concentrated by a
heliostat field and efficiently absorbed in a solar reactor that
thermochemically converts H2O and CO2 to syngas
which is subsequently processed to Fischer-Tropsch hydro-carbon fuels.
Solar-to-syngas energy conversion efficiencies exceeding 30% can
potentially be realized (11)) thanks to favorable thermodynamics at high temperature and utilization of the full solar spectrum . 12)

Expected Innovations

The following key innovations are expected from the SUN-to-LIQUID project:

• Pre-commercial integration of
all subsystems of the process chain to solar liquid fuels, namely: the
high-flux solar concentrator, the solar thermochemical reactor, and the
gas-to-liquid conversion unit.

The preceding EU-project SOLAR-JET has recently demonstrated the first-ever solar thermochemical kerosene production from H2O and CO2 in a laboratory environment. 13)
A total of 291 stable redox cycles were performed, yielding 700
standard liters of high-quality syngas, which was compressed and
further processed via Fischer-Tropsch synthesis to a mixture of
naphtha, gasoil, and kerosene. 14)

As a
follow-up project, SUN-to-LIQUID will design, fabricate, and
experimentally validate a more than 12-fold scale-up of the complete
solar fuel production plant and will establish a new milestone in
reactor efficiency. The field validation will integrate for the first
time the whole production chain from sunlight, H2O and CO2 to liquid hydrocarbon fuels.

3) A gas-to-liquid conversion subsystem
— Comprising compression and storage units for syngas and a
dedicated micro FT unit for the synthesis of liquid hydrocarbon fuels.

SUN-to-LIQUID will run a long-term
operation campaign: SUN-to-LIQUID will parametrically optimize the
solar thermochemical fuel plant on a daily basis over the time scale of
months under realistic steady-state and transient conditions relevant
to large-scale industrial implementation.

Concept and Approach

The SUN-to-LIQUID approach uses concentrated solar energy to synthesize liquid hydrocarbon fuels from H2O and CO2.
This reversal of combustion is accomplished via a high-temperature
thermochemical cycle based on metal oxide redox reactions which convert
H2O and CO2 into energy-rich synthesis gas (syngas), a mixture of mainly H2 and CO.15) This two-step cycle for splitting H2O and CO2 is schematically represented by:

The thermochemical process

Since H2/CO and O2 are formed in different steps, the problematic high-temperature fuel/O2
separation is eliminated. The net product is high-quality synthesis gas
(syngas), which is further processed to liquid hydrocarbons via
Fischer-Tropsch (FT) synthesis. FT synthetic paraffinic kerosene
derived from syngas is already certified for aviation.

SUN-to-LIQUID uses concentrated
solar radiation as the source of high-temperature process heat to drive
endothermic chemical reactions for solar fuel production. 16) A variety of redox active materials have been explored by different research groups. 17)
Among them, non-stoichiometric cerium oxide (ceria) has emerged as an
attractive redox active material because of its high oxygen ion
conductivity and cyclability, while maintaining its fluorite-type
structure and phase.

Reactor configuration

The laboratory-scale solar reactor
for a radiative power input of 4 kW has been designed, fabricated, and
experimentally demonstrated at ETH Zurich. The reactor configuration,
which was used in the FP7-project SOLAR-JET, is schematically shown in
Figure 6.

It consists of a cavity receiver containing a reticulated porous ceramic (RPC) foam-type structure made of pure CeO2 that was directly exposed to concentrated solar radiation. The production of H2 from H2O, CO from CO2, and high quality syngas suitable for FT synthesis by simultaneously splitting a mixture of H2O and CO2 has been demonstrated (Ref. 14).

The main objective of SUN-to-LIQUID
is the scale-up and experimental demonstration of the complete process
chain to solar liquid fuels from H2O and CO2 at a
pre-commercial size, i.e. moving from a 4 kW setup in the laboratory to
a 50 kW pre-commercial plant in the field. SUN-to-LIQUID will
demonstrate an enhanced solar-to-fuel energy conversion efficiency and
validate the field suitability.

SUN-to-LIQUID will demonstrate an enhanced solar-to-fuel energy conversion efficiency and validate the field suitability.

The high-flux solar concentrating
subsystem consists of an ultra-modular solar heliostat central receiver
that provides intense solar radiation for high temperature applications
beyond the capabilities of current commercial CSP installations. This
subsystem is constructed at IMDEA Energía at Móstoles
Technology Park, Madrid, in 2016. The customized heliostat field makes
use of most recent developments on small size heliostats and a tower
with reduced height (15 m) to minimize visual impact. The heliostat
field consists of 169 small size heliostats (1.9 m x 1.6 m). When all
heliostats are aligned, it is possible to fulfil the specified flux
above 2500 kW/m2 for at least 50 kW and an aperture of 16 cm, with a peak flux of 3000 kW/m2. A reliable road map for competitive drop-in fuel production from H2O, CO2, and solar energy will be established.

Figure 7: The SUN-to-LIQUID
project develops an alternative fuel technology that promises unlimited
renewable transportation fuel supply from water, CO2 and concentrated
sunlight. The project, which is funded by the EU and Switzerland, can
have important implications for the transportation sectors, especially
for the long-haul aviation and shipping sectors, which are strongly
dependent on hydrocarbon fuels (video credit: ARTTIC, Published on 12
June 2019)

SUN-to-LIQUID Field Test Project

The SUN-to-LIQUID four-year project,
which finishes at the end of this year, is supported by the EU’s
Horizon 2020 research and innovation program and the Swiss State
Secretariat for Education, Research and Innovation. It involves leading
European research organizations and companies in the field of solar
thermochemical fuel research. In addition to ETH Zurich, IMDEA Energy and HyGear Technology & Services, other partners include the German Aerospace Center (DLR) and Abengoa Energía. Project coordinator Bauhaus Luftfahrt is also responsible for technology and system analyses and ARTTIC International Management Services is supporting the consortium with project management and communication. 18)

The
preceding EU-project SOLAR-JET developed the technology and achieved
the first-ever production of solar jet fuel in a laboratory
environment. The SUN-to-LIQUID project scaled up this technology for
on-sun testing at a solar tower. For that purpose, a unique solar
concentrating plant was built at the IMDEA Energy Institute in
Móstoles, Spain. “A sun-tracking field of heliostats
concentrates sunlight by a factor of 2500 – three times greater
than current solar tower plants used for electricity generation,”
explains Manuel Romero of IMDEA Energy. This intense solar flux,
verified by the flux measurement system developed by the German
Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR)
makes it possible to reach reaction temperatures of more than 1500
ºC within the solar reactor positioned at the top of the tower. 19)

The solar
reactor, developed by project partner ETH Zurich, produces synthesis
gas, a mixture of hydrogen and carbon monoxide, from water and carbon
dioxide via a thermochemical redox cycle. An on-site gas-to-liquid
plant that was developed by the project partner HyGear processes this
gas to kerosene.

DLR has many years of experience in
the development of solar-thermal chemical processes and their
components. In the SUN-to-LIQUID project, DLR was responsible for
measuring the solar field and concentrated solar radiation, for
developing concepts for optimized heat recovery and – as in the
previous SOLAR-JET project – for computer simulations of the
reactor and the entire plant. Researchers from the DLR Institute of
Solar Research and the DLR Institute of Combustion Technology used
virtual models to scale up the solar production of kerosene from the
laboratory to a megawatt-scale plant and to optimize the design and
operation of the plant. For SUN-to-LIQUID, DLR solar researchers
developed a flux density measurement system that makes it possible to
measure the intensity of highly concentrated solar radiation directly
in front of the reactor with minimal interruption of its operation.
This data is necessary to operate the plant safely and to determine the
efficiency of the reactor.

Unlimited supply of sustainable fuel:
Compared to conventional fossil-derived jet fuel, the net carbon
dioxide emissions to the atmosphere can be reduced by more than 90
percent. Furthermore, since the solar energy-driven process relies on
abundant feedstock and does not compete with food production, it can
thus meet the future fuel demand at a global scale without the need to
replace the existing worldwide infrastructure for fuel distribution,
storage, and utilization.

Melting a satellite, a piece at a time

17 June 2019: Researchers took one
of the densest parts of an Earth-orbiting satellite, placed it in a
plasma wind tunnel then proceeded to melt it into vapor. Their goal was
to better understand how satellites burn up during reentry, to minimize
the risk of endangering anyone on the ground. 20)

Figure 9: A rod-shaped
magnetorquer – made of an external carbon fiber reinforced
polymer composite, with copper coils and an internal iron-cobalt core
– being melted at thousands of degrees C inside a DLR plasma wind
tunnel. This atmospheric reentry simulation was performed as part of
ESA's 'Design for Demise' efforts to reduce the risk of reentering
satellites reaching the ground (image credit: ESA/DLR)

Taking place as part of ESA’s
Clean Space initiative, the fiery testing occurred inside a plasma wind
tunnel, reproducing reentry conditions, at the DLR German Aerospace
Center’s site in Cologne.

The test subject was a magnetorquer,
designed to interact magnetically with Earth’s magnetic field to
shift satellite orientation.

Figure 10: Melting a piece of a
satellite. Researchers took one of the heaviest, bulkiest parts of an
Earth-orbiting satellite, placed it in a plasma wind tunnel, then
proceeded to melt it into vapor. Their goal was to better understand
how satellites burn up during reentry, to minimize the risk of
endangering anyone on the ground (video credit: ESA/DLR/Belstead
Research)

The mysterious crystal that melts at two different temperatures

06 June 2019: In a little-known
paper published in 1896, Emil Fischer—the German chemist who
would go on to win the 1902 Nobel Prize in Chemistry for synthesizing
sugars and caffeine—said his laboratory had produced a crystal
that seemed to break the laws of thermodynamics. To his puzzlement, the
solid form of acetaldehyde phenylhydrazone (APH) kept melting at two
very different temperatures. A batch he produced on Monday might melt
at 65 °C, while a batch on Thursday would melt at 100 °C. 21)

Colleagues
and rivals at the time told him he must have made a mistake. Fischer
didn’t think so. As far as he could tell, the crystals that
melted at such different points were identical. A few groups in Britain
and France repeated his work and got the same baffling results. But as
those scientists died off, the mystery was forgotten, stranded in
obscure academic journals published in German and French more than a
century ago.

There it would probably have
remained but for Terry Threlfall, an 84-year-old chemist at the
University of Southampton, UK. Stumbling across Fischer’s 1896
paper in a library about a decade ago, Threlfall was intrigued enough
to kick-start an international investigation of the mysterious crystal.
Earlier this year in the journal Crystal Growth and Design, Threlfall
and his colleagues published the solution: APH is the first recorded
example of a solid that, when it melts, forms two structurally distinct
liquids. Which liquid emerges comes down to contamination so subtle
that it’s virtually undetectable. 22)

he quest began in 2008 when
Threlfall, a fluent speaker of German and a keen student of the history
of science, was searching the pages of the 140-year-old Berichte der
deutschen chemischen Gesellschaft for interesting solid-state work
relevant to his research on second-order phase transitions. After
learning of the long-lost puzzle from Fischer’s paper, Threlfall
followed the reported recipe and found that his own samples of APH
melted according to the same peculiar pattern. One batch melted at
around 60 °C, the other at 90–95 °C.

As Fischer knew 125 years ago, the
laws of thermodynamics do not allow such a molecule. If a pair of
solids have different melting points, then they must be structurally
distinct. Yet all the modern structural analysis techniques that
Threlfall and some colleagues tried on Fischer’s compound
confirmed the 19th-century claim. X-ray diffraction, nuclear magnetic
resonance, IR spectroscopy: All showed the crystals that behaved so
differently were identical.

“For
two years we wondered whether to believe the evidence of our own eyes
and think that we needed to rewrite the laws of the universe, or to
believe thermodynamics and think that we were simply incompetent
experimentalists,” Threlfall says.

The first clue for solving the mystery came from the way APH crystals are prepared. The molecule (C8H10N2)
is made up of a benzene ring attached to a pair of nitrogen atoms, one
of which is attached to a hydrogen atom and a methyl group that can
point either up or down. Chemists make APH by dissolving solid
acetaldehyde (a precursor for many useful chemical reactions and a
compound found naturally in fruit) into aqueous ethanol and adding
drops of liquid phenylhydrazine (also first made and characterized by
Fischer, who used it in his seminal studies of sugars). If the mixture
is chilled and stirred, jagged flakes and then thicker chunks of APH
crystals start to appear.

Figure 13: Terry Threlfall and
his colleagues confirmed that there are low-melting-point and
high-melting-point forms of APH. The y axis represents the heat
absorbed in melting; the measured absorption is the area under the
curve (image credit: Terry Threlfall)

According
to reports from Fischer’s time, there were hints that impurities
could play a role in the puzzling behavior of APH. Adding drops of an
acid could steer the crystallization process toward the
low-melting-point version of the molecule; with added alkali, the
high-melting-point crystal would emerge. Threlfall confirmed that claim
and found that he could convert between the two forms. The low-melting
version could be made to melt at the higher temperature by exposing it
to ammonia vapor. And the high-melting crystal just needed a whiff of
acid to bring its melting point down.

That behavior seemed to suggest that
the acid worked like rock salt does in lowering the melting point of
water ice. But for salt to make a difference, a significant amount must
be added—certainly enough to show up in a close examination of
the ice’s structure. At as little as a thousandth of a molar
equivalent, the quantities of acid or alkali needed to make the switch
in APH were vanishingly small. Whatever contamination occurred did so
with no detectable physical change to the crystal structure.

Threlfall got some important help
from Hugo Meekes, a solid-state physicist at Radboud University in
Nijmegen, the Netherlands. After hearing of a 2012 lecture that
Threlfall had given about the conundrum, Meekes wondered if the
solution might relate to a different, but equally curious, phenomenon
called the disappearing polymorph problem. A scourge of drug companies,
the problem manifests as the production of a solid that’s
slightly but consequentially different from the desired product. The
polymorphs are identical except for varying crystalline structures,
which can give them different properties. In the late 1990s, for
example, Abbott Laboratories learned that it had produced a
less-soluble polymorph of its antiviral crystalline compound ritonavir.

The cause of disappearing polymorphs
is disputed, but Meekes says it seems to come down to imperceptible
contamination—perhaps a single molecule in the air can disrupt
the process by seeding crystallization of the problematic form.
“It sounds rather unbelievable, but it’s the only
explanation,” he says. “We thought the situation with the
APH must be something like this.”

But the APH case didn’t fit
the pattern. The crystals of APH that melted at different temperatures
weren’t polymorphs; they were identical. The researchers failed
to find any other structural discrepancies either. For example, some
molecules show different physical properties when their same atoms are
arranged in different patterns, which is called isomerization. But both
solid forms of APH contained the Z isomer, in which the methyl group
points down.

Meekes too was stumped.

Enter Manuel Minas da Piedade, a
solid-state physicist and thermodynamics researcher at the University
of Lisbon, whom Threlfall met at a conference in 2011. After initially
offering a hunch that led to another dead end, the Portuguese physicist
did what many scientists do when faced with something that
doesn’t add up: He went back to first principles. Because it is
impossible for the same material to melt at different temperatures if
the initial and final states are the same, he says, “either we
don’t have the same crystal state, or the final state cannot be
the same.”

Until then, all the tests performed
by Threlfall and a growing number of interested colleagues had focused
on solid APH, since differences in melting point typically stem from
differences in the solid form. But, out of options on the solid front,
in 2015 the researchers took a look at the liquids that emerged.

Back in the Netherlands, Meekes spun
tiny tubes of the hot, molten APH in a solid-state NMR machine, once
with the low-melting-point sample and once with the high-melting-point
one. Occasional forays to temperatures higher than the delicate
equipment’s 100 °C limit led to “frowning
technicians,” Meekes says, but the risk was worth it. He
discovered that the spectra of the two liquids were different. The same
solid crystal was melting to form two liquids with distinct
compositions—an unprecedented finding. “We think we have a
clue as to what’s going on,” Meekes recalls telling
Threlfall at a conference.

Figure 14: Study coauthors Simon
Coles (left) and Terry Threlfall performed some of their APH detective
work at the UK National Crystallography Service at the University of
Southampton (image credit: Simon Coles)

Tricky liquid

The difference, Meekes, Threlfall,
and colleagues soon found as they probed further, comes down to
isomerization, but only in the liquid phase. Although solid APH
consists of solely the Z isomer, liquid APH also contains E isomer, in
which the methyl group points up. In the liquid state, with the
molecules spaced farther apart and therefore with more room to
maneuver, APH can flit between the two forms, and it does so until it
finds the most stable mix. That turns out to be a blend of about
one-third of the Z isomer and two-thirds of the E form.

The relative amounts of each isomer
at equilibrium are determined by the molecules’ Gibbs free
energies, a measure of their thermodynamic potential. As the difference
in Gibbs energy increases, so does the ratio of one isomer to the
other. What makes APH so unusual, Threlfall says, is that the optimal
isomer combination for liquid APH doesn’t match that of the solid
form. “That the [solid] crystal is composed entirely of Z
molecules shows that these must have a more favorable packing,”
he says.

Tests showed that the high-melting
solid crystal melted to a liquid that was also all Z. Then the Z-type
molecules started to flip to E-type and continued until they hit that
stable mix. But when the low-melting solid APH melted, it did so almost
immediately to the stable mix of two-thirds E. The two liquids are
different—and so the melting points are different—only
because one represents an intermediate stage.

It was a melting-point suppression
effect, just like salt and ice, but it was much larger than anyone on
the team had thought possible. So what was behind it? Like the salt,
they thought it must be an impurity. And like the disappearing
polymorphs that plague the pharmaceutical industry, that impurity is
too small to see or measure. Threlfall says hydrogen ions must be
clinging to the surface of the solid crystal and catalyzing the shift
from the Z form to the E form. To do so, those protons shift the
electron density of the nitrogen atoms, which loosens the connection
between nitrogen and carbon atoms in the APH molecules from a strong
double bond to a weaker single one. The bond is therefore free to
rotate, allowing a much more rapid switch between the Z and E forms.

Figure 16: Two isomers of APH. As
a solid, molecules of APH take the Z form (left), in which the methyl
group points down. But liquid APH also contains the E isomer, in which
the methyl group points up (image credit: Leyla-Cann
Söğütoğlu and Hugo Meekes)

With no acid present, the Z-form
solid melts to Z-form liquid, and then this Z-form liquid starts the
transition to E-form liquid until it reaches the stable 1:2 ratio. But
when acid is there, the catalysis effect speeds the switch from Z form
to E form, so much so that it happens as the solid melts.

Overall,
the starting solid is the same, the finishing liquid is the same, and
the amount of energy used is the same. The laws of the universe are
safe. Gérard Coquerel, who works on thermodynamics and
solid-state physics at the University of Rouen, France, and was not
involved in the project, says it’s an important discovery that
organic chemists and others who rely on melting points to help
characterize compounds should take into account. “It shows that
sometimes there is a need to be careful about what we consider as the
melting point,” he says.

Fischer would have been delighted to
see the answer, Threlfall says, and the 19th-century chemist would
probably have understood it. Although the team’s work breaks
genuinely new ground, Meekes cheerfully admits that the circumstances
under which the melting-point suppression occurs are so specific that
the research is unlikely to have useful applications. The team
hasn’t even coined a name for the physical process by which
identical solids can melt into distinct liquids. “If someone else
wants to name it, then they can,” Threlfall says. “But if
you ask me, the scientific literature is already cluttered with too
many needless terms.”

Mission Control 'Saves Science'

17 May 2019: Every minute,
ESA’s Earth observation satellites gather dozens of gigabytes of
data about our planet – enough information to fill the pages on a
100-meter long bookshelf. Flying in low-Earth orbits, these spacecraft
are continuously taking the pulse of our planet, but it's teams on the
ground at ESA’s Operations Center in Darmstadt, Germany, that keep our explorers afloat. 23)

Figure 17: ESA has been dedicated
to observing Earth from space ever since the launch of its first
Meteosat weather satellite back in 1977. With the launch of a range of
different types of satellites over the last 40 years, we are better
placed to understand the complexities of our planet, particularly with
respect to global change. Today’s satellites are used to forecast
the weather, answer important Earth-science questions, provide
essential information to improve agricultural practices, maritime
safety, help when disaster strikes, and all manner of everyday
applications (image credit: ESA)

From flying groups of spacecraft in
complex formations to dodging space debris and navigating the
ever-changing conditions in space known as space weather, ESA’s
spacecraft operators ensure we continue to receive beautiful images and
vital data on our changing planet.

Get in formation

Many Earth observation satellites travel in formation. For example, the Copernicus Sentinel-5P satellite follows behind the Suomi-NPP
satellite (from the National Oceanic and Atmospheric Administration).
Flying in a loose trailing formation, they observe parts of our planet
in quick succession and monitor rapidly evolving situations. Together
they can also cross-validate instruments on board as well as the data
acquired.

ESA’s Earth Explorer Swarm
satellites are another example of complex formation flying. On a
mission to provide the best ever survey of Earth’s geomagnetic
field, they are made up of three identical satellites flying in what is
called a constellation formation.

Swarm’s individual satellites
operate together under shared control in a synchronized manner,
accomplishing the same objective of one giant – and more
expensive – satellite.

“Formation
flying has all the challenges of flying many single spacecraft, except
with the added complexity that we need to maintain a regular distance
between all of these high-speed and high-tech eyes on Earth,”
explains Jose Morales Santiago, ESA’s Head of the Earth
Observation Mission Operations Division. ”Every decision we make,
every command we send, has to be the right one for each spacecraft
– particularly when it comes to maneuvers. These must be planned
properly so that they do not endanger companion satellites, while
keeping a consistent configuration across the formation.”

Figure 18: Swarm is ESA's first
Earth observation constellation of satellites. The three identical
satellites are launched together on one rocket. Two satellites orbit
almost side-by-side at the same altitude – initially at about 460
km, descending to around 300 km over the lifetime of the mission. The
third satellite is in a higher orbit of 530 km and at a slightly
different inclination. The satellites’ orbits drift, resulting in
the upper satellite crossing the path of the lower two at an angle of
90° in the third year of operations. The different orbits along
with satellites’ various instruments optimize the sampling in
space and time, distinguishing between the effects of different sources
and strengths of magnetism (image credit: ESA/AOES Medialab)

Saving science

Last year, ESA’s Earth
observation missions performed a total of 28 ‘collision avoidance
maneuvers’. These maneuvers saw operators send the orders to a
spacecraft to get out of the way of an oncoming piece of space debris.

An impact with a fast-moving piece
of space junk has the potential to destroy an entire satellite and in
the process create even more debris. As a spacecraft
‘swerves’ to avoid collision, science instruments may need
to be turned off to ensure their safety and avoid being contaminated by
the thrusting engine.

Teams at mission control consider
how to keep Europe’s fleet of Earth observers safe while
maximizing the vital work they are able to do. Recently, they came up
with an ingenious concept to ‘save science’ during such
maneuvers of the Sentinel-5P satellite.

The Sentinel team quickly realized
that during a collision avoidance maneuver they would have to suspend
science collection for almost a day, because of the emergency firing of
the thrusters.

“That’s a lot of data to
miss out on. As the amount of space debris is currently increasing,
this would be something we would need to do more and more often,”
explains Pierre Choukroun, Sentinel-5P Spacecraft Operations Engineer,
who came up with the fix. “So we designed and validated a new
on-board function to enhance the spacecraft’s autonomy, such that
the science data loss is reduced to a bare minimum. We are very much
looking forward to securing more data for the science community in the
near future!”

With this new strategy, the science
instruments on Sentinel-5P would be shut off for around on hour
compared with an entire day!

Sun protection

As if dodging bits of space debris
weren’t enough for Europe’s Earth explorers, they also have
to navigate the turbulent weather conditions in space.

Space weather
refers to the environmental conditions around Earth due to the dynamic
nature of our Sun. The constant mood swings of our star influence the
functioning and reliability of our satellites in space, as well as
infrastructure on the ground.

Figure 19: SOHO's view of the
September 2017 solar flares. The Sun unleashed powerful solar flares on
6 September, one of which was the strongest in over a decade. An
M-class flare was also observed two days earlier on 4 September. The
flares were launched from a group of sunspots classified as active
region 2673. The shaded disc at the center of the image is a mask in
SOHO’s LASCO instrument that blocks out direct sunlight to allow
study of the faint details in the Sun's corona. The white circle added
within the disc shows the size and position of the visible Sun. (video
credit: SOHO (ESA & NASA)

When the Sun is particularly active,
it adds extra energy to Earth’s atmosphere, changing the density
of the air at low-Earth orbits. Increased energy in the atmosphere
means that satellites in this region experience more ‘drag’
– a force that acts in the opposite direction to the motion of
the spacecraft, causing it to decrease in altitude.

Operators need this information to
know when to perform maneuvers to “boost” the
satellite’s speed in order to counter drag and keep it in its
proper orbit.

This drag effect also changes the
speed and position of space debris around Earth, meaning our
understanding of the debris environment needs to be constantly updated
in light of changing space weather.

“While Earth observation
satellites monitor the weather on Earth, we have to stay aware of the
changing weather in space,” says Thomas Ormston, Spacecraft
Operations Engineer at ESA. “This is vital because understanding
atmospheric drag is fundamental to predicting when we will be
threatened by space debris and determining when and how big our
spacecraft maneuvers need to be to keep delivering great science to our
users.”

Space weather also impacts
communication between ground stations and satellites due to changes in
the upper atmosphere, the ionosphere, during solar events. Because of
this, satellite operators avoid critical satellite operations like
maneuvers or updates of the on board software during periods of high
solar activity.

Figure 20: It’s difficult
to comprehend the size and sheer power of our Sun, a churning ball of
hot gas has a mass that is 1.3 million times larger than Earth, it
dominates our Solar System. Unpredictable and temperamental, it blasts
intense radiation and colossal amounts of energetic material in every
direction, creating the ever-changing conditions in space known as
'space weather'. The solar wind is a constant stream of electrons,
protons and stripped-down atoms emitted by the Sun, while coronal mass
ejections are the Sun’s periodic outbursts of colossal clouds of
solar plasma. The most extreme of these events disturb Earth’s
protective magnetic field, creating geomagnetic storms at our planet.
— These storms can cause serious problems for modern
technological systems, disrupting or damaging satellites in space and
the multitude of services – like navigation and telecoms –
that rely on them, and blacking out power grids and radio
communication. They can even serve potentially harmful doses of
radiation to astronauts on future missions to the Moon or Mars (image
credit: ESA)

Testing satellite marker designs

24 April 2019: Akin to landing
lights for aircraft, ESA is developing infrared and phosphorescent
markers for satellites, to help future space servicing vehicles
rendezvous and dock with their targets. 24)

Developed by the Hungarian company Admatis (Advanced Materials in Space) as part of an ESA Clean Space
project, these markers would offer robotic space servicing vehicles a
steady target to home in on, providing critical information on the line
of sight, distance and pointing direction of their target satellite.

Figure
21: Initial testing of these ‘Passive Emitting Material at
end-of-life’ or PEMSUN markers took place at the end of March
2019 inside ESA’s GNC Rendezvous, Approach and Landing Simulator,
part of the Agency's Orbital Robotics and Guidance, Navigation and
Control Laboratory, at its ESTEC technical center in Noordwijk, the
Netherlands (image credit: ESA)

“The
idea itself is not new, but this is the first time we’ve
manufactured and tested sample patches, cut into spacecraft multi-layer
insulation covering,” comments ESA Clean Space trainee
Sébastien Perrault. “For the design we’ve looked into one larger pattern incorporating smaller versions for when the space servicing vehicle comes close enough that its camera’s field of view is filled.

“These markers would be very
useful during eclipse states for instance, when Earth obscures the Sun
in low Earth orbit, to allow the chaser vehicle to stay fixed on its
target, potentially in combination with radio tags.”

ESA is studying space servicing vehicles to carry out a wide range of roles in orbit, from refurbishment and refuelling to mission disposal at their end of life.

Figure 22:
GRALS Testbed. This robotic arm, attached to a 33 m track is ESA's
GRALS (GNC Rendezvous, Approach and Landing Simulator), is part of the
Agency's Orbital Robotics and Guidance, Navigation and Control
Laboratory. GRALS is used to simulate close approach and capture of
uncooperative orbital targets, such as drifting satellites or to
rendezvous with asteroids. It can also be used to test ideas for
descending to surfaces, such as a lunar or martian landing (image
credit: ESA, M. Grulich)

Legend to Figure 22:
The moveable arm can be equipped with cameras to test vision-based
software on a practical basis to close on a scale model of its target.
Image-processing algorithms recognize various features on the surface
of the model satellite seen here, and uses those features to calculate
the satellite’s tumble, allowing the chaser to safely come
closer. Alternatively, the robotic arm can be fitted with a gripper, to
test out actually securing a target, or with altimeters or other range
sensors.

Mirror array for LSS (Large Space Simulator)

17 April 2019: The mirror array (Figure 23) remains an integral element of ESA’s Large Space Simulator
at the ESTEC Test Center in Noordwijk, the Netherlands. It is used to
subject entire satellites to space-like conditions ahead of launch. At
15 m high and 10 m in diameter, the chamber is cavernous enough to
accommodate an upended double decker bus. 25)

Satellites are lowered down through
a topside hatch. Once the top and side hatches are sealed,
high-performance pumps create a vacuum a billion times lower than
standard sea level atmosphere, held for weeks at a time during test
runs.

This mirror array is made of 121 separate hexagonal segments. Its task is to reflect a 6-m diameter beam of simulated sunlight
into the chamber, at the same time as the walls are pumped full of
–190°C liquid nitrogen, together recreating the extreme
thermal conditions prevailing in orbit.

The LSS has tested dozens of space missions over the years, including many of ESA's largest: as well as BepiColombo, the 8-ton Envisat and the 20-ton Automated Transfer Vehicle.

Figure 23:
The giant 121-segment mirror array used to reflect simulated sunlight
into the largest vacuum chamber in Europe seen being hoisted into
position within ESA’s technical heart back in 1986 (image credit:
ESA, CC BY-SA 3.0 IGO)

Cold plasma tested on ISS

10 April 2019: Low-temperature
plasma – electrically charged gas – that was originally
tested aboard the International Space Station is now being harnessed to
kill drug-resistant bacteria and viruses that can cause infections in
hospital. 26)

Professor Gregor Morfill of Germany’s Max Planck Institute for Extraterrestrial Physics
made use of the ISS to investigate complex three-dimensional plasmas
that Earth gravity would have flattened. His very first plasma chamber
was installed aboard the Station back in 2001, by cosmonaut Sergei
Krikalev. The latest fourth-generation follow-on is still running on
the ISS to this day.

Plasmas are usually hot gases but
Prof. Morfill’s team developed a method of generating room
temperature ‘cold plasma’. Exposure to this forms small
holes in the membranes of bacterial cells and destroy their DNA, while
human cells are not so easily damaged.

So the idea was born to make use of
cold plasma against bacteria in infected wounds without harming the
patient. Initial treatment was for infected chronic wounds such as leg
ulcers. Initial clinical trials showed significant reduction in
bacterial burden of infected wounds, supporting healing and pain
relief.

Starting this May, this
‘plasma care’ device will be evaluated in a medical trial
across multiple German healthcare institutes.

Figure 24: Technology image of
the week: Cold plasma tested aboard the International Space Station is
now being harnessed against drug-resistant bacteria (image credit: Max
Planck Institute for Extraterrestrial Physics)

3D printing and milling Athena optic bench

03 April 2019: Twin robotic arms
work together as part of a project to construct what will be the
largest, most complex object ever 3D printed in titanium: a test
version of the 3-m diameter ‘optic bench’ at the heart of
ESA’s Athena X-ray observatory. 27)

Figure 25: Technology image of
the week: twin robotic arms work together to 3D print and mill a test
version of the optical heart of ESA’s Athena X-ray observatory
(image credit: Fraunhofer IWS)

- The first multi-axis robotic arm
builds up each new layer of metal using a laser to melt titanium
powder. The second robotic arm then immediately cuts away any
imperfections using a cryogenically cooled milling tool. The bench
itself is placed on a slowly moving 3.4 m diameter turntable.

-
“ESA has teamed up with Germany’s Fraunhofer Institute for
Material and Beam Technology for this exploratory activity,”
explains ESA materials and processes engineer Johannes Gumpinger.
“The final design of Athena’s optic bench is still to be
decided, but if it will be built in titanium then its size and
complexity is such that it could not be built in any other way.”

- Due to launch in 2031, ESA’s Athena
mission will probe 10 to 100 times deeper into the cosmos than previous
X-ray missions, to observe the very hottest, high-energy celestial
objects.

- The optic bench aligns and secures
around 750 mirror modules in a complex structure with many deep pockets
that tapers out to a maximum height of 30 cm. Its overall shape needs
to be precise down to a scale of a few tens of micrometers – or
thousandths of a centimeter.

- “Similarly, the entire
process has been designed to minimize any risk of contamination. The
titanium powder is swept into the laser using the noble gas argon that
also prevents any contamination with air. And the milling tool is kept
cool using liquid carbon dioxide that evaporates as it warms up,
preventing any harmful deposition on the freshly-laid metal
surface.”

- Precision sensors immediately
detect any out of tolerance elements for milling or more extensive
repair – including milling away for reprinting.

- Smaller segments have been
manufactured so far, with a 1.5 m diameter demonstrator optic bench set
to follow. The full scale 3 m bench is expected to take about a year to
produce.

- “It will be a huge task,
taking a lot of time and energy,” adds Johannes. “But if we
manage it, it will be the largest titanium object ever 3D printed
– and the process will be available to manufacture other large
parts, potentially in other metals.”

- Last month more than 150 experts from all across Europe met at ESA’s technical heart in the Netherlands to share the latest results
from ESA Advanced Manufacturing projects covering topics including 3D
printing and the latest composite materials as well as friction
stir-welding.

Figure 26:
3D printing titanium for Athena. A close-up view of laser melting being
used to 3D print in titanium to produce test versions of the
‘optic bench’ at the heart of our Athena X-ray observatory.
A multi-axis robotic arm is being used to produce the complex
structure, including deep pockets to place optical mirror modules
(video credit: Fraunhofer IWS)

Legend to Figure 26:
“The essential technological achievement is the fact that 3D
printing takes place under local protective gas shielding, without a
protective gas chamber,” comments André Seidel, overseeing
the project at the Fraunhofer Institute for Material and Beam
Technology in Germany. “This is enabled by a specially-developed
process head called COAXShield which uses the noble gas argon to sweep
titanium powder into the path of the laser, in the process protecting
the newly-printed titanium from contact with the atmosphere.”

The optic bench itself is placed on
a slowly moving 3.4-m diameter turntable between the two robotic arms.
The end goal of this ESA Technology Development Element project is to
produce a 3-m diameter optical bench, but in principle the procedure
can be applied to a wide variety of sizes.

“You can see the metallic
bright surface of the titanium, reflecting the honeycomb structure of
the protective gas nozzle,” adds André. “Taking
account of this for laser melting was a very big challenge, and an
absolute milestone in the project.”

Introduction of SmartSat architecture in spacecraft

20 March 2019: Lockheed Martin of
Denver, CO, announced a new generation of space technology launching
this year that will allow satellites to change their missions in orbit.
Satellites that launched one, ten or even fifteen years ago largely
have the same capability they had when they lifted off. That's changing
with new architecture that will let users add capability and assign new
missions with a software push, just like adding an app on a smartphone.
This new tech, called SmartSat, is a software-defined satellite architecture that will boost capability for payloads on several pioneering nanosats ready for launch this year. 28)

"Imagine a new type of satellite
that acts more like a smartphone. Add a SmartSat app to your satellite
in-orbit, and you've changed the mission," said Rick Ambrose, executive
vice president of Lockheed Martin Space. "We are the first to deploy
this groundbreaking technology on multiple missions. SmartSat will give
our customers unparalleled resiliency and flexibility for changing
mission needs and technology, and it unlocks even greater processing
power in space."

This year Lockheed Martin is
integrating SmartSat technology on ten programs and counting, including
the Linus and Pony Express nanosats, which will be the first to launch.
These are rapid-prototype, testbed satellites using internal research
and development funding, ready for 2019 launches on the first LM 50
nanosatellite buses:

• Pony Express builds
multiple 6U satellites destined for a low earth orbit and will space
qualify state-of-the-art networking technologies. Pony Express 1 is a
pathfinder for a software-defined payload that will test cloud
computing infrastructure and was developed in nine months. Follow-on
Pony Express missions will prove out RF-enabled swarming formations and
space-to-space networking.

"SmartSat is a major step forward in
our journey to completely transform the way we design, build and
deliver satellites," said Ambrose. "The LM 50 bus is the perfect
platform for testing this new, groundbreaking technology. We're
self-funding these missions to demonstrate a number of new capabilities
that can plug into any satellite in our fleet, from the LM 50 nanosat
to our flagship LM 2100. And the same technology not only plugs into
ground stations, improving space-ground integration, it will one day
connect directly with planes, ships and ground vehicles, connecting
front-line users to the power of space like never before."

Cyber security is at the core of
this new technology. SmartSat-enabled satellites can reset themselves
faster, diagnose issues with greater precision and back each other up
when needed, significantly enhancing resiliency. Satellites can also
better detect and defend against cyber threats autonomously, and
on-board cyber defenses can be updated regularly to address new
threats.

SmartSat uses a hypervisor to
securely containerize virtual machines. It's a technology that lets a
single computer operate multiple servers virtually to maximize memory,
on-board processing and network bandwidth. It takes advantage of
multi-core processing, something new to space. That lets satellites
process more data in orbit so they can beam down just the most critical
and relevant information—saving bandwidth costs and reducing the
burden on ground station analysts, and ultimately opening the door for
tomorrow's data centers in space.

SmartSat uses a high-power,
radiation-hardened computer developed by the National Science
Foundation's Center for Space, High-performance, and Resilient
Computing, or SHREC. Lockheed Martin helps fund SHREC research, and in
turn gains access to world-class technologies and student researchers.

15 March 2019: A new study from The
Australian National University (ANU) has found a number of 2D materials
can not only withstand being sent into space, but potentially thrive in
the harsh conditions. It could influence the type of materials used to
build everything from satellite electronics to solar cells and
batteries - making future space missions more accessible, and cheaper
to launch. 29)30)

PhD candidate and lead author Tobias
Vogl was particularly interested in whether the 2D materials could
withstand intense radiation.

"The space environment is obviously
very different to what we have here on Earth. So we exposed a variety
of 2D materials to radiation levels comparable to what we expect in
space," Mr Vogl said. "We found most of these devices coped really
well. We were looking at electrical and optical properties and
basically didn't see much difference at all."

During a satellite's orbit around
the Earth, it is subjected to heating, cooling, and radiation. While
there's been plenty of work done demonstrating the robustness of 2D
materials when it comes to temperature fluctuations, the impact of
radiation has largely been unknown - until now.

The ANU team carried out a number of
simulations to model space environments for potential orbits. This was
used to expose 2D materials to the expected radiation levels. They
found one material actually improved when subjected to intense gamma
radiation.

"A material getting stronger after
irradiation with gamma rays - it reminds me of the hulk," Mr Vogl said.
"We're talking about radiation levels above what we would see in space
- but we actually saw the material become better, or brighter."

Mr Vogl says this specific material
could potentially be used to detect radiation levels in other harsh
environments, like near nuclear reactor sites.

"The applications of these 2D
materials will be quite versatile, from satellite structures reinforced
with graphene - which is five-times stiffer than steel - to lighter and
more efficient solar cells, which will help when it comes to actually
getting the experiment into space."

Among the
tested devices were atomically thin transistors. Transistors are a
crucial component for every electronic circuit. The study also tested
quantum light sources, which could be used to form what Mr Vogl
describes as the "backbone" of the future quantum internet.

"They could be used for
satellite-based long-distance quantum cryptography networks. This
quantum internet would be hacking proof, which is more important than
ever in this age of rising cyber attacks and data breaches."

"Australia is already a world leader
in the field of quantum technology," senior author Professor Ping Koy
Lam said. "In light of the recent establishment of the Australian Space
Agency, and ANU's own Institute for Space, this work shows that we can
also compete internationally in using quantum technology to enhance
space instrumentation."

Light from Exotic Crystal Semiconductor Could Lead to Better Solar Cells

15 March 2019: Scientists have found
a new way to control light emitted by exotic crystal semiconductors,
which could lead to more efficient solar cells and other advances in
electronics, according to a Rutgers-led study in the journal Materials
Today. 31)32)

Figure 29: A conceptual view of a
transistor device that controls photoluminescence (the light red cone)
emitted by a hybrid perovskite crystal (the red box) that is excited by
a blue laser beam after voltage is applied to an electrode (the gate),
image credit: Vitaly Podzorov and Yaroslav Rodionov

Their discovery involves crystals
called hybrid perovskites, which consist of interlocking organic and
inorganic materials, and they have shown great promise for use in solar
cells. The finding could also lead to novel electronic displays,
sensors and other devices activated by light and bring increased
efficiency at a lower cost to manufacturing of optoelectronics, which
harness light.

The Rutgers-led team found a new way
to control light (known as photoluminescence) emitted when perovskites
are excited by a laser. The intensity of light emitted by a hybrid
perovskite crystal can be increased by up to 100 times simply by
adjusting voltage applied to an electrode on the crystal surface.

“To the best of our knowledge,
this is the first time that the photoluminescence of a material has
been reversibly controlled to such a wide degree with voltage,”
said senior author Vitaly Podzorov, a professor in the Department of
Physics and Astronomy in the School of Arts and Sciences at Rutgers
University–New Brunswick. “Previously, to change the
intensity of photoluminescence, you had to change the temperature or
apply enormous pressure to a crystal, which was cumbersome and costly.
We can do it simply within a small electronic device at room
temperature.”

Semiconductors like these
perovskites have properties that lie between those of the metals that
conduct electricity and non-conducting insulators. Their conductivity
can be tuned in a very wide range, making them indispensable for all
modern electronics.

“All the wonderful modern
electronic gadgets and technologies we enjoy today, be it a smartphone,
a memory stick, powerful telecommunications and the internet,
high-resolution cameras or supercomputers, have become possible largely
due to the decades of painstaking research in semiconductor
physics,” Podzorov said.

Understanding
photoluminescence is important for designing devices that control,
generate or detect light, including solar cells, LED lights and light
sensors. The scientists discovered that defects in crystals reduce the
emission of light and applying voltage restores the intensity of
photoluminescence.

Hybrid perovskites are more
efficient and much easier and cheaper to make than standard commercial
silicon-based solar cells, and the study could help lead to their
widespread use, Podzorov said. An important next step would be to
investigate different types of perovskite materials, which may lead to
better and more efficient materials in which photoluminescence can be
controlled in a wider range of intensities or with smaller voltage, he
said.

The study included lead author Hee
Taek Yi in Rutgers’ Department of Physics and Astronomy and
co-authors Assistant Research Professor Sylvie Rangan and Professor
Robert A. Bartynski, department chair. Researchers at the University of
Minnesota and University of Texas at Dallas contributed to the study.

Converting Wi-Fi Signals to Electricity with New 2-D Materials

•
8 March 2019: Devices that convert AC electromagnetic waves into DC
electricity are known as “rectennas.” MIT Researchers have
demonstrated a new kind of rectenna, that uses a flexible
radio-frequency (RF) antenna to capture electromagnetic waves —
including those carrying Wi-Fi. The antenna is connected to a novel
device made out of a two-dimensional semiconductor just a few atoms
thick, which converts the AC signal into a DC voltage. In this way, the
battery-free device passively captures and transforms ubiquitous Wi-Fi
(Wireless Fidelity) signals into useful DC power. Moreover, the device
is flexible and can be fabricated in a roll-to-roll process to cover
very large areas. 33)34)35)

Figure 30: Researchers from MIT
and elsewhere have designed the first fully flexible, battery-free
"rectenna" -- a device that converts energy from Wi-Fi signals into
electricity — that could be used to power flexible and wearable
electronics, medical devices, and sensors for the "internet of things"
(image credit: Christine Daniloff)

- “What if we could develop
electronic systems that we wrap around a bridge or cover an entire
highway, or the walls of our office and bring electronic intelligence
to everything around us? How do you provide energy for those
electronics?” says paper co-author Tomás Palacios, a
professor in the Department of Electrical Engineering and Computer
Science and director of the MIT/MTL Center for Graphene Devices and 2D
Systems in the Microsystems Technology Laboratories. “We have
come up with a new way to power the electronics systems of the future
— by harvesting Wi-Fi energy in a way that’s easily
integrated in large areas — to bring intelligence to every object
around us.”

- Promising early applications for
the proposed rectenna include powering flexible and wearable
electronics, medical devices, and sensors for the “internet of
things.” Flexible smartphones, for instance, are a hot new market
for major tech firms. In experiments, the researchers’ device can
produce about 40 µW of power when exposed to the typical power
levels of Wi-Fi signals (around 150 µW). That’s more than
enough power to light up an LED or drive silicon chips.

- Another possible application is
powering the data communications of implantable medical devices, says
co-author Jesús Grajal, a researcher at the Technical University
of Madrid. For example, researchers are beginning to develop pills that
can be swallowed by patients and stream health data back to a computer
for diagnostics.

- “Ideally you don’t
want to use batteries to power these systems, because if they leak
lithium, the patient could die,” Grajal says. “It is much
better to harvest energy from the environment to power up these small
labs inside the body and communicate data to external computers.”

- All rectennas rely on a component
known as a “rectifier,” which converts the AC input signal
into DC power. Traditional rectennas use either silicon or gallium
arsenide for the rectifier. These materials can cover the Wi-Fi band,
but they are rigid. And, although using these materials to fabricate
small devices is relatively inexpensive, using them to cover vast
areas, such as the surfaces of buildings and walls, would be
cost-prohibitive. Researchers have been trying to fix these problems
for a long time. But the few flexible rectennas reported so far operate
at low frequencies and can’t capture and convert signals in
gigahertz frequencies, where most of the relevant cell phone and Wi-Fi
signals are.

- To build their rectifier, the researchers used a novel 2-D material called molybdenum disulfide (MoS2),
which at three atoms thick is one of the thinnest semiconductors in the
world. In doing so, the team leveraged a singular behavior of MoS2:
When exposed to certain chemicals, the material’s atoms rearrange
in a way that acts like a switch, forcing a phase transition from a
semiconductor to a metallic material. The resulting structure is known
as a Schottky diode, which is the junction of a semiconductor with a
metal.

- “By engineering MoS2
into a 2-D semiconducting-metallic phase junction, we built an
atomically thin, ultrafast Schottky diode that simultaneously minimizes
the series resistance and parasitic capacitance,” says first
author and EECS postdoc Xu Zhang, who will soon join Carnegie Mellon
University as an assistant professor.

- Parasitic capacitance is an
unavoidable situation in electronics where certain materials store a
little electrical charge, which slows down the circuit. Lower
capacitance, therefore, means increased rectifier speeds and higher
operating frequencies. The parasitic capacitance of the
researchers’ Schottky diode is an order of magnitude smaller than
today’s state-of-the-art flexible rectifiers, so it is much
faster at signal conversion and allows it to capture and convert up to
10 gigahertz of wireless signals.

- “Such a design has allowed a
fully flexible device that is fast enough to cover most of the
radio-frequency bands used by our daily electronics, including Wi-Fi,
Bluetooth, cellular LTE, and many others,” Zhang says.

- The reported work provides
blueprints for other flexible Wi-Fi-to-electricity devices with
substantial output and efficiency. The maximum output efficiency for
the current device stands at 40 percent, depending on the input power
of the Wi-Fi input. At the typical Wi-Fi power level, the power
efficiency of the MoS2 rectifier is about 30 percent. For
reference, today’s rectennas made from rigid, more expensive
silicon or gallium arsenide achieve around 50 to 60 percent.

- “This very nice teamwork
from MIT demonstrates the first real application [of] atomically thin
semiconductors for a flexible rectenna for energy harvesting,”
says Philip Kim, a professor of physics and applied physics at Harvard
University whose research focuses on 2-D materials. “I am amazed
by the innovate approach that the team has set up to utilize the waste
energy from RF power around us.”

- The team is now planning to build
more complex systems and improve efficiency. The work was made
possible, in part, by a collaboration with the Technical University of
Madrid through the MIT International Science and Technology Initiatives
(MISTI). It was also partially supported by the Institute for Soldier
Nanotechnologies, the Army Research Laboratory, the National Science
Foundation’s Center for Integrated Quantum Materials, and the Air
Force Office of Scientific Research.

NICU (Neonatal Intensive Care Units)

•
28 February 2019: An interdisciplinary Northwestern University team
(Chicago and Evanston, Illinois) has developed a pair of soft, flexible
wireless body sensors that replace the tangle of wire-based sensors
that currently monitor babies in hospitals’ neonatal intensive
care units (NICU) and pose a barrier to parent-baby cuddling and
physical bonding. 36)37)

The team recently completed a
collection of first human studies on premature babies at Prentice
Women’s Hospital and the Ann & Robert H. Lurie
Children’s Hospital in Chicago and concluded that the wireless
infant sensors provided data as precise and accurate as that from
traditional monitoring systems. The wireless patches also are gentler
on a newborn’s fragile skin and allow for more skin-to-skin
contact with the parent.

The study includes initial data from
more than 20 babies who wore the wireless sensors alongside traditional
monitoring systems, so Northwestern researchers could do a
side-by-side, quantitative comparison. Since then, the team has
conducted successful tests with more than 70 babies in the NICU.

The study — involving
materials scientists, engineers, dermatologists and pediatricians, was
published in the journal Science. 38)

The study includes initial data from
more than 20 babies who wore the wireless sensors alongside traditional
monitoring systems, so Northwestern researchers could do a
side-by-side, quantitative comparison. Since then, the team has
conducted successful tests with more than 70 babies in the NICU.

“We
wanted to eliminate the rat’s nest of wires and aggressive
adhesives associated with existing hardware systems and replace them
with something safer, more patient-centric and more compatible with
parent-child interaction,” says John A. Rogers, a bioelectronics
pioneer, who led the technology development. “Our wireless,
battery-free, skin-like devices give up nothing in terms of range of
measurement, accuracy and precision — and they even provide
advanced measurements that are clinically important but not commonly
collected.”

Cutting the cords: The mass of wires
that surround newborns in the NICU are often bigger than the babies
themselves. Typically five or six wires connect electrodes on each baby
to monitors for breathing, blood pressure, blood oxygen, heartbeat and
more. Although these wires ensure health and safety, they constrain the
baby’s movements and pose a major barrier to physical bonding
during a critical period of development.

“We know that skin-to-skin
contact is so important for newborns — especially those who are
sick or premature,” says Paller, a pediatric dermatologist.
“It’s been shown to decrease the risk of pulmonary
complications, liver issues and infections. Yet, when you have wires
everywhere and the baby is tethered to a bed, it’s really hard to
make skin-to-skin contact.”

The benefits of the Northwestern
team’s new technology reach beyond its lack of wires —
measuring more than what’s possible with today’s clinical
standards.

The dual wireless sensors monitor
babies’ vital signs — heart rate, respiration rate and body
temperature — from opposite ends of the body. One sensor lies
across the baby’s chest or back, while the other sensor wraps
around a foot. This strategy allows physicians to gather an
infant’s core temperature as well as body temperature from a
peripheral region.

“Differences in temperature
between the foot and the chest have great clinical importance in
determining blood flow and cardiac function,” Rogers says.
“That’s something that’s not commonly done
today.”

• March 2019: 5G mobile
telecommunication standards stand for fifth-generation advancements
made in the mobile communications field. These comprise packet switched
wireless systems using orthogonal frequency division multiplexing
(OFDM) with wide area coverage, high throughput at millimeter waves (10
mm to 1 mm) covering a frequency range of 30 GHz to 300 GHz, and
enabling a 20 Mbit/s data rate to distances up to 2 km. The
millimeter-wave band is the most effective solution to the recent surge
in wireless Internet usage. These specifications are capable of
providing ‘wireless world wide web’ (WWWW) applications. 39)

Users of 5G technology can download
an entire film to their tablets or laptops, including 3D movies; they
can download games and avail of remote medical services. With the
advent of 5G, Piconet and Bluetooth technologies will become outdated.
The 5G mobile phones would be akin to tablet PCs, where you could watch
TV channels at HD clarity without any interruption.

Chronological evolution of mobile technologies:
Although the 1G system (NMT) was introduced in 1981, 2G (GSM) started
to come out in 1982, and 3G (W-CDMA)/FOMA first appeared in 2001, the
complete development of these standards (e.g., IMT-2000 and UMTS) took
almost 10 years. It is still unclear how much time it will take to
launch the standards for 5G.

5G technology will ensure the
convergence of networks, technologies, applications and services, and
can serve as a flexible platform. Wireless carriers will have an
opportunity to shorten their return-on-investment periods, improve
operating efficiency and increase revenues. In short, this will change
people’s lives in numerous ways.

In 2019, after years of hype about
Gb (gigabit) speeds that will let you download full-length movies in
mere seconds, 5G is close to becoming a reality. Last year gave us a
taste of 5G as Verizon launched a home broadband service using the
next-generation wireless technology and AT&T brought 5G service to
a dozen cities. 40)

The fifth generation of
connectivity, pithily called 5G, will be ready for prime time this
year. Software is being tested, hardware is in the works, and carriers
are readying their plans to flip the switch on their 5G network in the
first half of 2019.

The new networking standard is not
just about faster smartphones. Higher speeds and lower latency will
also make new experiences possible in augmented and virtual reality,
connected cars and the smart home — any realm where machines need
to talk to each other constantly and without lag.

Where 5G Is Now:

The 3rd Generation Partnership Project, the standards body that writes the rules for wireless connectivity, agreed in late 2017 on the first specification for 5G.
The Non-Standalone Specification of 5G New Radio standard covers 600
and 700 MHz bands and the 50 GHz millimeter-wave end of the spectrum.
That agreement paved the way for hardware makers to start developing
handsets with 5G modems inside. But the non-standalone specification
applies to 5G developed with LTE as an anchor.

In June of 2018, the standards body
completed the rules for standalone 5G. Network operators are now
fine-tuning their software using equipment that complies with the
completed standard.

"[The standard] really sets [the
stage] for interoperable systems and field trials with operators in
2018, and it starts the clock for being able to build
standards-compliant devices heading toward the last half of 2018 and
early 2019 launches,” Qualcomm's Matt Branda, who oversees 5G
marketing, told us last year.

It's important to note that 5G
devices have to play nice with existing LTE networks, because in areas
where 5G coverage will be spotty or nonexistent, the new radios will be
optimized for available LTE connections. That's why the non-standalone
specification came down first.

Companies such as Qualcomm and Intel
are working on 5G modems that will fit into phones, cars, smart-home
devices and other device forms that have yet to take shape. Those
radios are in the midst of testing to make sure they're interoperable
with network operators and infrastructure companies.

Space's part in the 5G revolution

The communications industry is in a
period of unprecedented change, and consumers and enterprises across
all regional and demographic sectors increasingly view mobile
connectivity – and mobile broadband specifically – as an
essential part of everyday life and business. 41)

5G represents an opportunity for the
mobile industry to address that phenomenon. While the transition from
3G to 4G was an evolution in speed that paved the way for mobile
broadband services, 5G is a revolution – an entirely new
architecture that delivers exponential improvements in not only speed,
but also latency, capacity, power consumption and number of connections
supported. This opens the door to a broad new range of use cases, from
enhanced mobile broadband to massive machine-type communications to
ultra-low latency communications.

The Third
Generation Partnership Project (3GPP), the industry association driving
5G development, is studying the challenges and has identified the value
satellite coverage can bring to the enablement of 5G use cases,
particularly mission-critical and industrial applications where
ubiquitous coverage is crucial. By partnering with satellite operators,
MNOs (Mobile Network Operators) can expand their footprint into regions
that are difficult or impossible to serve via their terrestrial assets.
Satellite represents a path for mobile network operators to expand
their footprint and thus deliver on the promise of seamless, universal
5G coverage and services.

Figure 33: 5G, the next
generation of communication services, will deliver ultra-fast speeds,
connect all people and devices to the internet and minimize delays. It
will affect everybody, changing the way we communicate, work and
interact with technology. Space has an invaluable role to play in the
5G ecosystem. Satellites can extend, enhance, and provide reliability
and security to 5G like no other, helping to deliver its promise of
global, ubiquitous connectivity, with no noticeable difference to the
end-user. ESA’s Satellite for 5G (S45G) program aims to promote
the value-added benefits of space to 5G, by developing and
demonstrating integrated satellite- and terrestrial-based 5G services,
across multiple markets and use cases (video credit: ESA) 42)

NASA to Advance Unique 3D Printed Sensor Technology

• 15 February 2019: A NASA
technologist is taking miniaturization to the extreme. Mahmooda Sultana
won funding to advance a potentially revolutionary, nanomaterial-based
detector platform. The technology is capable of sensing everything from
minute concentrations of gases and vapor, atmospheric pressure and
temperature, and then transmitting that data via a wireless antenna
— all from the same self-contained platform that measures just
two-by-three-inches in size. 43)

Under a $2 million technology
development award, Sultana and her team at NASA’s Goddard Space
Flight Center in Greenbelt, Maryland, will spend the next two years
advancing the autonomous multifunctional sensor platform. If
successful, the technology could benefit NASA’s major science
disciplines and efforts to send humans to the Moon and Mars. These tiny
platforms could be deployed on planetary rovers to detect small
quantities of water and methane, for example, or be used as monitoring
or biological sensors to maintain astronaut health and safety.

Central to the effort, funded by
NASA’s Space Technology Mission Directorate’s (STMD) Early
Career Initiative (ECI) is a 3D printing system developed by Ahmed
Busnina and his group at Northeastern University in Boston. The 3D
printing system is like printers used to produce money or newspapers.
However, instead of ink, the printer applies nanomaterials,
layer-by-layer, onto a substrate to create tiny sensors. Ultimately,
each is capable of detecting a different gas, pressure level or
temperature.

Nanomaterials, such as carbon nanotubes,
graphene, molybdenum disulfide and others, exhibit interesting physical
properties. They are highly sensitive and stable at extreme conditions.
They are also lightweight, hardened against radiation and require less
power, making them ideal for space applications, Sultana said.

Under her partnership with
Northeastern University, Sultana and her group will design the sensor
platform, determining which combination of materials are best for
measuring minute, parts-per-billion concentrations of water, ammonia,
methane and hydrogen — all important in the search for life
throughout the solar system. Using her design, Northeastern University
will then use its Nanoscale Offset Printing System to apply the
nanomaterials. Once printed, Sultana’s group will functionalize
the individual sensors by depositing additional layers of nanoparticles
to enhance their sensitivity, integrate the sensors with readout
electronics, and package the entire platform.

The approach differs dramatically
from how technologists currently fabricate multifunctional sensor
platforms. Instead of building one sensor at a time and then
integrating it to other components, 3D printing allows technicians to
print a suite of sensors on one platform, dramatically simplifying the
integration and packaging process.

Figure 34: Technologist Mahmooda
Sultana holds an early iteration of an autonomous multifunctional
sensor platform, which could benefit all of NASA's major scientific
disciplines and efforts to send humans to the Moon and Mars Image
credit: NASA/W. Hrybyk)

Also innovative is Sultana’s
plan to print on the same silicon wafer partial circuitry for a
wireless communications system that would communicate with ground
controllers, further simplifying instrument design and construction.
Once printed, the sensors and wireless antenna will be packaged onto a
printed circuit board that holds the electronics, a power source, and
the rest of the communications circuitry.

“The
beauty of our concept is that we’re able to print all sensors and
partial circuity on the same substrate, which could be rigid or
flexible. We eliminate a lot of the packaging and integration
challenges,” Sultana said. “This is truly a multifunctional
sensor platform. All my sensors are on same chip, printed one after
another in layers.”

Wide-Ranging Uses: The
research picks up where other NASA-funded efforts ended. Under several
previous efforts funded by Goddard’s Internal Research and
Development Program and STMD’s Center Innovation Fund, Sultana
and her team used the same technique to manufacture and demonstrate
individual sensors made of carbon nanotubes and molybdenum disulfide,
among other materials. “The sensors were found to be quite
sensitive, down to low parts per million. With our ECI funding, we are
targeting the instrument’s sensitivity to parts per billion by
improving sensor design and structure,” Sultana said.

According to her, the project
addresses NASA’s need for low-power, small, lightweight, and
highly sensitive sensors that can distinguish important molecules other
than by measuring the masses of a molecule’s fragments, which is
how many missions currently detect molecules today using mass
spectrometers.

In fact, the agency has acknowledged
that future sensors need to detect minute concentrations of gases and
vapors in the parts per billion level. Although mass spectrometers can
detect a wide spectrum of molecules — particularly useful for
unknown samples — they have difficulty distinguishing between
some of the important species, such as water, methane and ammonia.
“It’s also difficult to reach the parts per billion or
beyond level with them,” she said.

“We’re really excited
about the possibilities of this technology,” Sultana said.
“With our funding, we can take this technology to the next level
and potentially offer NASA a new way to create customized,
multifunctional sensor platforms, which I believe could open the door
to all types of mission concepts and uses. The same approach we use to
identify gases on a planetary body also could be used to create
biological sensors that monitor astronaut health and the levels of
contaminants inside spacecraft and living quarters.”

The prototype sensor, developed in
collaboration with NASA’s Goddard Space Flight Center in
Greenbelt, Maryland, employs a revolutionary measurement technique
called atom interferometry, which former U.S. Energy Department
Secretary Steven Chu and his colleagues invented in the late 1980s. In
1997, Chu received the Nobel Prize in Physics for his work.

Since the discovery, researchers
worldwide have attempted to build practical, compact, more sensitive
quantum sensors, such as atom interferometers, that scientists could
use in space-constrained areas, including spacecraft.

Figure 36: This image
demonstrates the control that the Goddard-AOSense team has over the
paths of atoms. In this demonstration, they manipulated the path to
form the acronym, NASA (image credit: AOSense, Inc.)

With funding from NASA’s Small
Business Innovation Research, Instrument Incubator, and Goddard’s
Internal Research and Development programs, the Goddard-AOSense team
developed an atom-optics gravity gradiometer primarily for mapping
Earth’s time-varying gravitational field. Although Earth’s
gravitational field changes for a variety of reasons, the most
significant cause is a change in water mass. If a glacier or an ice
sheet melts, this would affect mass distribution and therefore
Earth’s gravitational field.

“Our sensor is smaller than
competing sensors with similar sensitivity goals,” said Babak
Saif, a Goddard optical physicist and collaborator in the effort.
“Previous atom interferometer-based instruments included
components that would literally fill a room. Our sensor, in dramatic
comparison, is compact and efficient. It could be used on a spacecraft
to obtain an extraordinary data set for understanding Earth’s
water cycle and its response to climate change. In fact, the sensor is
a candidate for future NASA missions across a variety of scientific
disciplines.”

Atom interferometry, however, hinges
on quantum mechanics, the theory that describes how matter behaves at
sub-microscopic scales. Atoms, which are highly sensitive to
gravitational signals, can also be cajoled into behaving like light
waves. Special pulsing lasers can split and manipulate atom waves to
travel different paths. The two atom waves will interact with gravity
in a way that affects the interference pattern produced once the two
waves recombine. Scientists can then analyze this pattern to obtain an
extraordinarily accurate measure of the gravitational field.

In particular, the team is eying its
quantum sensor as a potential technology to gather the type of data
currently produced by NASA’s Gravity Recovery and Climate
Experiment (GRACE) Follow-On mission. GRACE-FO is a two-satellite
mission that has generated monthly gravity maps showing how mass is
distributed and how it changes over time. Due to its extraordinary
precision, the quantum sensor could eliminate the need for a
two-satellite system or provide even greater accuracy if deployed on a
second satellite in a complementary orbit, said Lee Feinberg, a Goddard
optics expert also involved in the effort.

“With this new technology, we
can measure the changes of Earth’s gravity that come from melting
ice caps, droughts, and draining underground water supplies, greatly
improving on the pioneering GRACE mission,” said John Mather, a
Goddard scientist and winner of the Nobel Prize in Physics in 2006 for
his work on NASA’s Cosmic Background Explorer that helped cement
the big-bang theory of the universe.

The instrument, however, could be used to answer other scientific questions.

“We can measure the interior
structure of planets, moons, asteroids, and comets when we send probes
to visit them. The technology is so powerful that it can even extend
the Nobel-winning measurements of gravitational waves from distant
black holes, observing at a new frequency range,” Mather said,
referring to the confirmation in 2015 of cosmic gravitational waves
— literally, ripples in the fabric of space-time that radiate out
in all directions, much like what happens when a stone is thrown into a
pond. Since that initial confirmation, the Laser Interferometer
Gravitational Wave Observatory and the European Virgo detectors have
detected other events.

Since 2004, AOSense has developed
quantum sensors and atomic clocks, with broad expertise and
capabilities spanning all aspects of development and characterization
of advanced sensors for precision navigation and timing. 45)

Figure 37: Real-world atomic
sensors and other exacting applications require laser sources with
specific size, environmental, and optical characteristics, placing
unique constraints that most commercial laser systems do not meet.
AOSense has developed a line of external cavity diode lasers (ECDLs)
designed to meet these needs, offering narrow linewidth in a compact
package (image credit: AOSense)

Our AOSense ECDL is built on a
semi-monolithic bench with a cat’s-eye design for stable
operation in demanding environments. The wavelength is factory-set to
the desired user wavelength; no subsequent mechanical adjustment is
required. A PZT may be used for ~GHz tuning in addition to current and
temperature controls. Current wavelengths include alkali (767 nm, 780
nm, 852 nm) and alkaline earth (423 nm, 461 nm, 657 nm, 689 nm, 698 nm)
transitions. Additional UV/blue models at 369 and 399 nm are currently
in development. The flexible design is fully translatable to additional
wavelengths. The output beam is circularized to optimize fiber coupling
(not available for all wavelengths). The compact laser enclosure
dimensions are only 7.5 x 3.8 x 2.8 cm.

New Standard for Wireless Transmission Speed at 100 Gbit/s

•
22 August 2018: Northrop Grumman Corporation and DARPA (Defense
Advanced Research Projects Agency) have set a new standard for wireless
transmission by operating a data link at 100 Gbit/s over a distance of
20 kilometers in a city environment. 46)

The 100G system is capable of rate
adaptation on a frame by frame basis from 9 to 102 Gbit/s to maximize
data rate throughout dynamic channel variations. Extensive link
characterization demonstrated short-term error-free performance from 9
to 91 Gbit/s, and a maximum data rate of 102 Gbit/s with 1 erroneous
bit received per ten thousand bits transmitted.

The successful data link results
from the integration of several key technologies. The link operates at
millimeter wave frequencies (in this case, 71-76 GHz and 81-86 GHz with
5 GHz of bandwidth, or data carrying capacity, and uses a bandwidth
efficient signal modulation technique to transmit 25 Gbit/s data
streams on each 5 GHz channel. To double the rate within the fixed
bandwidth, the data link transmits dual orthogonally polarized signals
from each antenna. Additionally, the link transmits from two antennas
simultaneously (spatial multiplexing) and uses
multiple-input-multiple-output (MIMO) signal processing techniques to
separate the signals at the two receiving antennas, thus again doubling
the data rate within the fixed bandwidth.

According to Louis Christen,
director, research and technology, Northrop Grumman, “This
dramatic improvement in data transmission performance could
significantly increase the volume of airborne sensor data that can be
gathered and reduce the time needed to exploit sensor data. Next
generation sensors such as hyperspectral imagers typically collect data
faster, and in larger quantity than most air-to-ground data links can
comfortably transmit,” said Christen. “Without such a high
data rate link data would need to be reviewed and analyzed after the
aircraft lands.”

By
contrast, a 100G data link could transmit high-rate data directly from
the aircraft to commanders on the ground in near real time, allowing
them to respond more quickly to dynamic operations.

The successful 100G ground
demonstration sets the stage for the flight test phase of the 100G RF
Backbone program. This next phase, which started in June, demonstrates
the 100G air-to-ground link up to 100 Gbit/s over a 100 km range and
extended ranges with lower data rates. The 100G hardware will be flown
aboard the Proteus demonstration aircraft developed by Northrop Grumman
subsidiary Scaled Composites.

Northrop Grumman’s 100G
industry team includes Raytheon, which developed the millimeter wave
antennas and related RF electronics and Silvus Technologies, which
provides the key spatial multiplexing and MIMO signal processing
technologies.

Researchers develop novel process to 3D print one of the strongest materials on Earth

• 15 August 2018: Researchers
from Virginia Tech (Blacksburg, VA) and Lawrence Livermore National
Laboratory (Livermore, CA) have developed a novel way to 3D print
complex objects of one of the highest-performing materials used in the
battery and aerospace industries. 47)

Previously, researchers could only
print this material, known as graphene, in 2D sheets or basic
structures. But Virginia Tech engineers have now collaborated on a
project that allows them to 3D print graphene objects at a resolution
an order of magnitude greater than ever before printed, which unlocks
the ability to theoretically create any size or shape of graphene.

Because of its strength - graphene
is one of the strongest materials ever tested on Earth - and its high
thermal and electricity conductivity, 3D printed graphene objects would
be highly coveted in certain industries, including batteries,
aerospace, separation, heat management, sensors, and catalysis.

Graphene is a single layer of carbon
atoms organized in a hexagonal lattice. When graphene sheets are neatly
stacked on top of each other and formed into a three-dimensional shape,
it becomes graphite, commonly known as the “lead” in
pencils.

Because graphite is simply
packed-together graphene, it has fairly poor mechanical properties. But
if the graphene sheets are separated with air-filled pores, the
three-dimensional structure can maintain its properties. This porous
graphene structure is called a graphene aerogel.

“Now a designer can design
three-dimensional topology comprised of interconnected graphene
sheets,” said Xiaoyu “Rayne” Zheng, assistant
professor with the Department of Mechanical Engineering in the College
of Engineering and director of the Advanced Manufacturing and
Metamaterials Lab. “This new design and manufacturing freedom
will lead to optimization of strength, conductivity, mass transport,
strength, and weight density that are not achievable in graphene
aerogels.”

Zheng, also an affiliated faculty
member of the Macromolecules Innovation Institute, has received grants
to study nanoscale materials and scale them up to lightweight and
functional materials for applications in aerospace, automobiles, and
batteries.

Previously, researchers could print
graphene using an extrusion process, sort of like squeezing toothpaste,
but that technique could only create simple objects that stacked on top
of itself. “With that technique, there’s very limited
structures you can create because there’s no support and the
resolution is quite limited, so you can’t get freeform
factors,” Zheng said. “What we did was to get these
graphene layers to be architected into any shape that you want with
high resolution.”

This project began three years ago
when Ryan Hensleigh, lead author of the article and now a third-year
Macromolecular Science and Engineering Ph.D. student, began an
internship at the LLNL (Lawrence Livermore National Laboratory in
Livermore), California. Hensleigh started working with Zheng, who was
then a member of the technical staff at Lawrence Livermore National
Laboratory. When Zheng joined the faculty at Virginia Tech in 2016,
Hensleigh followed as a student and continued working on this project.

To create these complex structures,
Hensleigh started with graphene oxide, a precursor to graphene,
crosslinking the sheets to form a porous hydrogel. Breaking the
graphene oxide hydrogel with ultrasound and adding light-sensitive
acrylate polymers, Hensleigh could use projection
micro-stereolithography to create the desired solid 3D structure with
the graphene oxide trapped in the long, rigid chains of acrylate
polymer. Finally, Hensleigh would place the 3D structure in a furnace
to burn off the polymers and fuse the object together, leaving behind a
pure and lightweight graphene aerogel.

“It’s a significant
breakthrough compared to what’s been done,” Hensleigh said.
“We can access pretty much any desired structure you want.”

The key finding of this work, which
was recently published with collaborators at LLNL in the journal
Materials Horizons, is that the researchers created graphene structures
with a resolution an order of magnitude finer than ever printed.
Hensleigh said other processes could print down to 100 µm, but
the new technique allows him to print down to 10 µm in
resolution, which approaches the size of actual graphene sheets. 48)

“We’ve been able to show
you can make a complex, three-dimensional architecture of graphene
while still preserving some of its intrinsic prime properties,”
Zheng said. “Usually when you try to 3D print graphene or scale
up, you lose most of their lucrative mechanical properties found in its
single sheet form.”

Figure 40: (A) Four
‘‘Green’’ MAG parts of differing unit-cell
structures before pyrolysis from left to right octet-truss, gyroid,
cubo-octahedron, and Kelvin foam; (B) optical image of pyrolyzed
gyroid; (C) SEM image of pyrolyzed gyroid with intricate overhang
structures (D) zoomed image of pyrolyzed gyroid in
‘‘C’’; (E) optical image of pyrolyzed MAG
octet-truss, of a different design than shown in
‘‘A’’ supported by a single strawberry blossom
filament; (F) SEM image of pyrolyzed octet-truss MAG in
‘‘E’’; (G) zoomed image of octet-truss in
‘‘E’’ showing the very high 10 µm
resolution achievable in our process (image credit:3D print graphene study team of Virginia Tech and Lawrence Livermore National Laboratory)

Prototype nuclear battery packs 10 times more power

• May 2018: Russian researchers
from the Moscow Institute of Physics and Technology (MIPT), the
Technological Institute for Superhard and Novel Carbon Materials
(TISNCM), and the National University of Science and Technology, MISIS,
have optimized the design of a nuclear battery generating power from
the beta decay of nickel-63 (63Ni), a radioactive isotope.
Their new battery prototype packs about 3,300 mW-hours of energy per
gram, which is more than in any other nuclear battery based on 63Ni,
and 10 times more than the specific energy of commercial chemical
cells. The paper was published in the journal Diamond and Related
Materials. 49)50)

Figure 41: A nuclear battery (image credit: Elena Khavina/MIPT)

Ordinary batteries powering clocks,
flashlights, toys, and other electrical devices use the energy of
so-called redox chemical reactions in which electrons are transferred
from one electrode to another via an electrolyte. This gives rise to a
potential difference between the electrodes. If the two battery
terminals are then connected by a conductor, electrons start flowing to
remove the potential difference, generating an electric current.
Chemical batteries, also known as galvanic cells, are characterized by
a high power density—that is, the ratio between the power of the
generated current and the volume of the battery. However, chemical
cells discharge in a relatively short time, limiting their applications
in autonomous devices. Some of these batteries, called accumulators,
are rechargeable, but even they need to be replaced for charging. This
may be dangerous, as in the case of a cardiac pacemaker, or even
impossible, if the battery is powering a spacecraft.

Fortunately, chemical reactions are
just one of the possible sources of electric power. In 1913, Henry
Moseley invented the first power generator based on radioactive decay.
His nuclear battery consisted of a glass sphere silvered on the inside
with a radium emitter mounted at the center on an isolated electrode.
Electrons resulting from the beta decay of radium caused a potential
difference between the silver film and the central electrode. However,
the idle voltage of the device was way too high—tens of kV
(kilovolt)—and the current was too low for practical
applications.

In 1953, Paul Rappaport proposed the
use of semiconducting materials to convert the energy of beta decay
into electricity. Beta particles—electrons and
positrons—emitted by a radioactive source ionize atoms of a
semiconductor, creating uncompensated charge carriers. In the presence
of a static field of a p-n structure, the charges flow in one
direction, resulting in an electric current. Batteries powered by beta
decay came to be known as betavoltaics. The chief advantage of
betavoltaic cells over galvanic cells is their longevity. Radioactive
isotopes used in nuclear batteries have half-lives ranging from tens to
hundreds of years, so their power output remains nearly constant for a
very long time. Unfortunately, the power density of betavoltaic cells
is significantly lower than that of their galvanic counterparts.
Despite this, betavoltaics were used in the 1970s to power cardiac
pacemakers, before being phased out by cheaper lithium-ion batteries,
even though the latter have shorter lifetimes.

Betavoltaic
power sources should not be confused with RTGs (Radioisotope
Thermoelectric Generators), which are also called nuclear batteries,
but operate on a different principle. Thermoelectric cells convert the
heat released by radioactive decay into electricity using
thermocouples. The efficiency of RTGs is only several percent and
depends on temperature. But owing to their longevity and relatively
simple design, thermoelectric power sources are widely used to power
spacecraft such as the New Horizons probe and Mars rover Curiosity.
RTGs were previously used on unmanned remote facilities such as
lighthouses and automatic weather stations. However, this practice was
abandoned, because used radioactive fuel was hard to recycle and leaked
into the environment.

A research team led by Vladimir
Blank, the director of TISNCM and chair of nanostructure physics and
chemistry at MIPT, came up with a way of increasing the power density
of a nuclear battery almost tenfold. The physicists developed and
manufactured a betavoltaic battery using nickel-63 as the source of
radiation and Schottky barrier-based diamond diodes for energy
conversion. The prototype battery achieved an output power of about 1
µW (microwatt), while the power density per cubic centimeter was
10 µW, which is enough for a modern artificial pacemaker.
Nickel-63 has a half-life of 100 years, so the battery packs about
3,300 mW-hours of power per 1 gram—10 times more than
electrochemical cells.

The nuclear battery prototype
consisted of 200 diamond converters interlaid with nickel-63 and stable
nickel foil layers (Figure 42). The
amount of power generated by the converter depends on the thickness of
the nickel foil and the converter itself, because both affect how many
beta particles are absorbed. Currently available prototypes of nuclear
batteries are poorly optimized, since they have excessive volume. If
the beta radiation source is too thick, the electrons it emits cannot
escape it. This effect is known as self-absorption. However, as the
source is made thinner, the number of atoms undergoing beta decay per
unit time is proportionally reduced. Similar reasoning applies to the
thickness of the converter.

The goal of the researchers was to
maximize the power density of their nickel-63 battery. To do this, they
numerically simulated the passage of electrons through the beta source
and the converters. It turned out that the nickel-63 source is at its
most effective when it is 2 µm thick, and the optimal thickness
of the converter based on Schottky barrier diamond diodes is around 10
µm.

Manufacturing technology:

The main technological challenge was
the fabrication of a large number of diamond conversion cells with
complex internal structure. Each converter was merely tens of
micrometers thick, like a plastic bag in a supermarket. Conventional
mechanical and ionic techniques of diamond thinning were not suitable
for this task. The researchers from TISNCM and MIPT developed a unique
technology for synthesizing thin diamond plates on a diamond substrate
and splitting them off to mass-produce ultrathin converters.

The team
used 20 thick boron-doped diamond crystal plates as the substrate. They
were grown using the temperature gradient technique under high
pressure. Ion implantation was used to create a 100 nm thick defective,
"damaged" layer in the substrate at the depth of about 700 nm. A
boron-doped diamond film 15 µm thick was grown on top of this
layer using chemical vapor deposition. The substrate then underwent
high-temperature annealing to induce graphitization of the buried
defective layer and recover the top diamond layer. Electrochemical
etching was used to remove the damaged layer. Following the separation
of the defective layer by etching, the semi-finished converter was
fitted with ohmic and Schottky contacts.

All converters were connected in parallel in a stack as shown in Figure 42.
The technology for rolling 2 µm thick nickel foil was developed
at the Research Institute and Scientific Industrial Association LUCH.
The battery was sealed with epoxy.

The prototype battery is characterized by the current-voltage curve shown in Figure 44.
The open-circuit voltage and the short-circuit current are 1.02 V and
1.27 µA, respectively. The maximum output power of 0.93 µW
is obtained at 0.92 volts. This power output corresponds to a specific
power of about 3,300 mW-hours per gram, which is 10 times more than in
commercial chemical cells or the previous nickel-63 nuclear battery
designed at TISNCM.

In 2016, Russian researchers from
MISIS had already presented a prototype betavoltaic battery based on
nickel-63. Another working prototype, created at TISNCM and LUCH, was
demonstrated at Atomexpo 2017. It had a useful volume of 1.5 cm3.

The main setback in commercializing
nuclear batteries in Russia is the lack of nickel-63 production and
enrichment facilities. However, there are plans to launch nickel-63
production on an industrial scale by mid-2020s.

There is an alternative radioisotope
for use in nuclear batteries: Diamond converters could be made using
radioactive carbon-14, which has an extremely long half-life of 5,700
years. Work on such generators was earlier reported by physicists from
the University of Bristol (UK).

The work reported in this story has prospects for medical applications. Most state-of-the-art cardiac pacemakers are over 10 cm3
in size and require about 10 µW of power. This means that the new
nuclear battery could be used to power these devices without any
significant changes to their design and size. "Perpetual pacemakers"
whose batteries need not be replaced or serviced would improve the
quality of life of patients.

The space industry would also
greatly benefit from compact nuclear batteries. In particular, there is
a demand for autonomous wireless external sensors and memory chips with
integrated power supply systems for spacecraft. Diamond is one of the
most radiation-proof semiconductors. Since it also has a large bandgap,
it can operate in a wide range of temperatures, making it the ideal
material for nuclear batteries powering spacecraft.

The researchers are planning to
continue their work on nuclear batteries. They have identified several
lines of inquiry that should be pursued. Firstly, enriching nickel-63
in the radiation source would proportionally increase battery power.
Secondly, developing a diamond p-i-n structure with a controlled doping
profile would boost voltage and therefore could increase the power
output of the battery at least by a factor of three. Thirdly, enhancing
the surface area of the converter would increase the number of
nickel-63 atoms on each converter.

TISNCM Director Vladimir Blank, who
is also chair of nanostructure physics and chemistry at MIPT, commented
on the study: "The results so far are already quite remarkable and can
be applied in medicine and space technology, but we are planning to do
more. In the recent years, our institute has been rather successful in
the synthesis of high-quality doped diamonds, particularly those with
n-type conductivity. This will allow us to make the transition from
Schottky barriers to p-i-n structures and thus achieve three times
greater battery power. The higher the power density of the device, the
more applications it will have. We have decent capabilities for
high-quality diamond synthesis, so we are planning to utilize the
unique properties of this material for creating new radiation-proof
electronic components and designing novel electronic and optical
devices."

The Kilopower Project of NASA

17 January 2018: When astronauts
someday venture to the Moon, Mars and other destinations, one of the
first and most important resources they will need is power. A reliable
and efficient power system will be essential for day-to-day
necessities, such as lighting, water and oxygen, and for mission
objectives, like running experiments and producing fuel for the long
journey home. 51)

That’s why NASA is conducting
experiments on Kilopower, a new power source that could provide safe,
efficient and plentiful energy for future robotic and human space
exploration missions. This pioneering space fission power system could
provide up to 10 kW of electrical power — enough to run two
average households — continuously for at least ten years. Four
Kilopower units would provide enough power to establish an outpost.

Currently, power is usually
generated in space by solar arrays that convert the Sun’s energy
into electricity or by radioisotope power systems that convert the heat
from naturally decaying plutonium238 into electricity. Solar or
radioisotope power systems may be impractical for future NASA missions
to places where sunlight is dim or unavailable, and where more than a
few hundreds of watts of power are needed. 52)

Fission power from nuclear reactors
could provide abundant energy anywhere that humans or our robotic
science probes might go. Fission, the splitting of an atom’s
nucleus, releases a great amount of heat energy: 1 pound of uranium
fuel can produce as much energy as about 3 million pounds of burnable
coal. With such a high energy density, fission power systems present an
ideal solution for space missions that require large amounts of power,
especially where sunlight is limited or not available.

Technology Demonstration Goal:
Because of fission power’s great potential for space exploration,
the NASA Space Technology Mission Directorate’s Game Changing
Development (GCD) Program is funding the Kilopower project, an effort
led by NASA’s Glenn Research Center to demonstrate space fission
power systems technology. Building on prior work by a joint NASA and
Department of Energy team, the project’s main goal is to assemble
and test an experimental prototype of a space fission power system. In
2012, Los Alamos National Laboratory and NASA Glenn demonstrated how an
innovative, small-scale heat pipe-cooled fission reactor could provide
electrical power using Stirling power conversion. This proof of physics
demonstration provided the basis for the Kilopower project, the goal of
which is to demonstrate the readiness of a monolithic-core heat-pipe
reactor power system for use in NASA’s exploration missions.

Accomplishing the Goal: The
NS (Nuclear Systems) Kilopower project is a partnership between NASA
and the Department of Energy’s National Nuclear Security
Administration (NNSA). Together, NASA and NNSA have designed and
developed a 1 kWe reactor prototype with technology that is relevant
for systems up to 10 kWe. It consists of a highly enriched uranium core
built by NNSA, heat pipes provided by Advanced Cooling Technologies
through a NASA Small Business Innovation Research contract, and
Stirling generators provided by Sunpower, Inc. The core is a solid
block of a uranium alloy, and heat pipes are clamped around the core to
transfer heat to Stirling power conversion units to generate electrical
power. Much smaller than terrestrial nuclear plants, Kilopower systems
are small enough to be demonstrated here on Earth in existing
facilities at the Nevada National Security Site.

Space Exploration Uses for Fission Power:
The Kilopower project was initiated because NASA mission planning
includes exploration of places in the solar system—such as deep
space beyond Jupiter’s orbit and the surfaces of Earth’s
moon and Mars—where power generation from sunlight is difficult
and power from radioisotope systems is limited by the fuel supply. For
human exploration, multiple 10 kWe Kilopower systems could provide the
40 kWe initially estimated to be needed by NASA’s preliminary
concepts for a human outpost, with the ability to add power as the
outpost grows. For robotic exploration, 1 kWe Kilopower units enable
abundant, reliable power for science and communications, and the
potential to field deep space missions based on science return while
conserving the limited supply of radioisotope fuel for its best
opportunities. Characteristics of fission power that make it so
beneficial for Mars outposts and deep space robotics also apply to
other space missions. Nuclear fission systems could be scaled up to
power nuclear electric propulsion vehicles to efficiently transport
heavy cargo beyond Mars, and they could potentially shorten crewed trip
times to Mars and other distant planets.

Game Changing Development Program:
The Game Changing Development (GCD) program is part of NASA’s
Space Technology Mission Directorate. The GCD program aims to advance
exploratory concepts and deliver technology solutions that enable new
capabilities or radically alter current approaches.

Unlike previous technologies, the
Kilopower reactor is simple, inexpensive and relies on fuels and
technologies that are already well understood, NASA officials said. It
uses active nuclear fission, like a conventional nuclear reactor, which
will enable it to harvest far more energy from its uranium alloy core
than an RTG (Radioisotope Thermoelectric Generator) could. A heat pipe
clamped around the reactor core will transfer heat to the unit's power
generators: small Stirling engines, a technology that was developed in
1816. The engines are simple pistons that convert heat into motion,
which is then converted to electricity. The reactor will radiate excess
heat from an umbrella-like cooling array.

• On 2 May 2018, NASA announced
the results of the KRUSTY experiment during a news conference at GRC
(Glenn Research Center). The Kilopower experiment was conducted
November 2017 through March 2018 at the Nevada National Security Site
(NNSS). 53)

- NASA and the Department of
Energy’s National Nuclear Security Administration (NNSA) have
successfully demonstrated a new nuclear reactor power system that could
enable long-duration crewed missions to the Moon, Mars and destinations
beyond.

-
“Safe, efficient and plentiful energy will be the key to future
robotic and human exploration,” said Jim Reuter, NASA’s
acting associate administrator for the Space Technology Mission
Directorate (STMD) in Washington. “I expect the Kilopower project
to be an essential part of lunar and Mars power architectures as they
evolve.”

- Kilopower is a small, lightweight
fission power system capable of providing up to 10 kW of electrical
power - enough to run several average households - continuously for at
least 10 years. Four Kilopower units would provide enough power to
establish an outpost.

- The prototype power system uses a
solid, cast uranium-235 reactor core, about the size of a paper towel
roll. Passive sodium heat pipes transfer reactor heat to
high-efficiency Stirling engines, which convert the heat to
electricity.

- According to David Poston, the
chief reactor designer at NNSA’s Los Alamos National Laboratory,
the purpose of the recent experiment in Nevada was two-fold: to
demonstrate that the system can create electricity with fission power,
and to show the system is stable and safe no matter what environment it
encounters. “We threw everything we could at this reactor, in
terms of nominal and off-normal operating scenarios and KRUSTY passed
with flying colors,” said Poston.

- The Kilopower team conducted the
experiment in four phases. The first two phases, conducted without
power, confirmed that each component of the system behaved as expected.
During the third phase, the team increased power to heat the core
incrementally before moving on to the final phase. The experiment
culminated with a 28-hour, full-power test that simulated a mission,
including reactor startup, ramp to full power, steady operation and
shutdown.

- Throughout the experiment, the
team simulated power reduction, failed engines and failed heat pipes,
showing that the system could continue to operate and successfully
handle multiple failures.

- “We put the system through
its paces,” said Gibson. “We understand the reactor very
well, and this test proved that the system works the way we designed it
to work. No matter what environment we expose it to, the reactor
performs very well.”

- The Kilopower project is
developing mission concepts and performing additional risk reduction
activities to prepare for a possible future flight demonstration. The
project will remain a part of the STMD’s Game Changing
Development program with the goal of transitioning to the Technology
Demonstration Mission program in Fiscal Year 2020.

- Such a demonstration could pave
the way for future Kilopower systems that power human outposts on the
Moon and Mars, including missions that rely on In-situ Resource Utilization to produce local propellants and other materials.

Figure 46: Artist's concept of new fission power system on the lunar surface (image credit: NASA)

• Testing: As of September 2017 a test reactor has been constructed, called KRUSTY
(Kilopower Reactor Using Stirling Technology). It is designed to
produce up to 1 kW of electric power and is about 1.9 m tall. The goal
of the KRUSTY experiment is to closely match the operational parameters
that would be required in NASA deep space missions. The prototype
Kilopower uses a solid, cast uranium-235 reactor core, about the size
of a paper towel roll. Reactor heat is transferred via passive sodium
heat pipes, with the heat being converted to electricity by Stirling
engines. 54)

- Testing to gain TRL 5 started in
November 2017 and continued into 2018. The first tests used a depleted
uranium core manufactured by Y-12 National Security Complex in Tennessee.
The depleted uranium core is exactly the same material as the regular
high-enriched uranium (HEU) core with the only difference being the
level of uranium enrichment. The testing of KRUSTY represents the first
time the United States has conducted ground tests on any space reactor
since the SNAP-10A experimental reactor was tested and eventually flown
in 1965.

Figure
47: Marc Gibson, Kilopower lead engineer, and Jim Sanzi, Vantage
Partners, install hardware on the Kilopower assembly at the Nevada
National Security Site in March 2018 (image credit: NASA) 55)

Top Tomatoes thanks to Mars Missions

11 April 2018: Inspired by an Obama
speech in 2010 on human missions to Mars, the Dutch company Groen Agro
Control started investigating the best way to grow and fertilize plants
in space, and whether that could also lead to improving the growth of
vegetables on Earth. 56)

“In space, you can fertilize
plants only with the minerals you take with you, but you still want
them to produce the best possible crops,” explains the
company’s Lex de Boer. “Ideally, you would also use the
water that evaporates from the plants as a source of drinking water,
with the minimum amount of purification. That means you have to apply
doses of each mineral extremely carefully, so that as little as
possible ends up unused in the drain water.”

To study this, the company built an
enclosed system in which tomato and pepper plants received doses of 16
different minerals, looking at how the uptake of each mineral
correlated with growth.

In 2013, the company met an ESA team
at the Space-MATCH event organized by Netherlands Organization for
Applied Scientific Research TNO and ESA’s Technology Transfer
Office to bring ESA engineers and industry together to exchange
knowhow. Here, the company was inspired to spin off a smart service
helping horticulturalists to fertilize plants better on Earth.

Figure 48: Next time you eat a
tomato or sweet pepper, take a closer look, because there’s a
good chance that its healthy appearance is thanks to one of former US
President Barack Obama’s speeches and ESA research for sending
people on long-duration space missions (image credit: M. Barel (CC
BY-NC 2.0))

To study the optimal dosing of
minerals for growing tomato and pepper plants, Dutch Groen Agro Control
built an enclosed system in which the plants received doses of 16
different minerals. The doses of each mineral were extremely carefully
controlled, so that as little as possible ends up unused in the drain
water.

Triggered by the requirement to provide for the needs of humans on long missions to the Moon and Mars, ESA’s MELiSSA (Micro-Ecological Life Support System Alternative)
project focuses on a ‘closed’ life support system, where
all supplies are reused and recycled. So, for example, organic waste
and carbon dioxide should be entirely converted into oxygen, water and
food.

“MELiSSA recognizes that we
have to develop a self-supporting system for long missions, as
astronauts will not be able to rely on regular deliveries of supplies,
especially as they move further from Earth,” explains ESA’s
Christel Paille. “One key issue is food and water supplies.
Astronauts will need to grow their own food with limited resources, and
reclaim as much water as possible from that growth cycle. Hence
it’s vital that we develop a scheme that tells them exactly the
right amount of fertilizer to apply at every stage in the plant
growth.”

Figure 50:
The AlgoSolis facility is offering researchers and industry an
opportunity to experiment with microalgae on larger scales than before.
Based in Saint-Nazaire, France, the site is a stepping stone to
industrial production of algae-based products (image credit:
Université de Nantes) 57)

Legend to Figure 50:
Microalgae offer huge benefits because they promise many products for
human use, from biofuels to oxygen and food, as well as clean
contaminated water or extract carbon dioxide from the atmosphere. ESA's
MELiSSA project is using algae and other organisms and chemicals to
develop a compact closed ecosystem to keep astronauts alive on long
missions.

Spin-off from research as if in space

Based on its initial experiments,
and the results it gained from growing vegetables in closed and
well-controlled environments conceptually as if in space, the company
developed a scheme for horticulturists, this time with the goal of
maximizing plant growth and yield through very careful use of
fertilizers.

In the service now offered to
growers, samples are taken every week of both the fertilizer solution
dripped into the plants – including tomatoes, peppers, cucumbers,
eggplant, roses and gerbera – and the liquid that drains away.

These are analyzed at the
company’s laboratory and the results sent back to the growers,
with advice on any changes they should make to the amounts of each of
the 16 minerals given to the plants.

“There is a separate approach
for each mineral, but these are also linked with each other because the
uptake of certain minerals – such as potassium, magnesium and
calcium – are closely related,” says Lex. “The amount
of each mineral that a plant needs also varies across its lifecycle. It
will need a different combination when it is producing stalks and
leaves early in its life compared with when it is producing flowers and
fruit.”

Horticulturalists
also face challenges in altering fertilizer doses to match changing
growing conditions. For example, rising energy prices have encouraged
growers to keep greenhouse windows closed. However, this causes higher
humidity, resulting in a fall in evaporation from plants.

That, in turn, makes it harder for
tomato plants to transport calcium to the top of the plant, which can
result in a condition that leaves and the plant top becomes necrotic.
The company’s scheme shows growers how to compensate for this by
altering not just the amount of calcium in the drop water, but also
magnesium and potassium levels.

Production increase: In less
than one season, Dutch customer Zwingrow has already started to see
positive results from using the scheme for its crop of orange bell
peppers.

“We’re always trying to
improve the health and quality of the plants we grow, but using this
weekly analysis means we are acting proactively, delving deeper into
the needs of the plants and getting better results,” says Ted
Zwinkels, co-owner of Zwingrow. “Even though we started using it
after the start of the season last year, the plants grew better and
were healthier. I’d estimate that overall production increased by
around 5%. It’s impossible to know how much of this was due to
the new regime, as variations in sunlight from year to year also play a
part. However, already this season, using the service from the very
start, we’ve seen stronger, better plants, and fewer vulnerable
ones.”

Groen Agro Control now has clients
across the world. While it still has plans for experiments on crop
growth in space, it is also widening its horizons on Earth, including a
potential service for crops grown outside using drop water application
of fertilizers, such as asparagus.

Production of NEXT-C ion propulsion engine

• 10 April 2018: Aerojet
Rocketdyne's (Redmond WA) NEXT-C ion propulsion engine has successfully
cleared NASA's CDR (Critical Design Review), confirming the technology
achieved all program requirements and is ready for final production of
the flight units. NEXT-C (NASA's Evolutionary Xenon Thruster-Commercial)
was developed by NASA and is being commercialized by Aerojet
Rocketdyne. NEXT-C has 7 kW of maximum power and an Isp > 4100 s.
Its high Isp (Specific Impulse) and flexible operational capabilities
make NEXT ideal for scientific space missions. 58)

NEXT-C will be the ion thruster used
on a 2021 mission, named DART (Double Asteroid Redirection Test), led
by the Johns Hopkins University Applied Physics Laboratory for NASA.
DART is a kinetic impact mission designed to collide with a moonlet
around the Didymos asteroid and slightly alter its orbit. This mission
will be a critical step in demonstrating NASA's impact threat
mitigation capabilities for redirection of a potentially hazardous
object such as an asteroid.

"Serving as the primary propulsion
source for DART, NEXT-C will establish a precedent for future use of
electric propulsion to enable ambitious future science missions," said
Eileen Drake, CEO and President of Aerojet Rocketdyne. "Electric
propulsion reduces overall mission cost without sacrificing reliability
or mission success."

Under a cost-sharing agreement with
NASA's Science Mission Directorate through the agency's Glenn Research
Center, Aerojet Rocketdyne is developing the NEXT-C electric propulsion
engine and power processing unit. In addition to DART, additional
NEXT-C units may be launched on future NASA planetary missions.

New dimension in design

• 11 April 2018: An alternative to conventional circuit boards, these 3D-molded interconnect devices (Figure 51)
add electrical connectivity to the surface of three-dimensional
structures. The aim is to combine mechanical, electronic and
potentially optical functions in a single 3D part, allowing the
creation of intricate, precisely aligned designs using fewer parts
while delivering significant savings in space and weight compared to
conventional electronic manufacturing. 59)

“These prototype interconnect
devices were produced using injection-moulded plastics incorporating
electrical metallisation,” explains ESA’s Jussi Hokka.
“In principle, however, other materials can also be used,
allowing the incorporation of sensors or the integration of shielding
or cooling systems.”

• 5 April 2018: A new method to
sensitively measure the structure of molecules has been demonstrated by
twisting laser light and aiming it at miniscule gold gratings to
separate out wavelengths. The technique could potentially be used to
probe the structure and purity of molecules in pharmaceuticals,
agrochemicals, foods and other important products more easily and
cheaply than existing methods. 60)

Developed by physicists at the
University of Bath (Bath UK), working with colleagues at the University
of Cambridge and UCL (University College London), the technique relies
on the curious fact that many biological and pharmaceutical molecules
can be either 'left-handed' or 'right-handed'.

Figure 52: A twisted laser beam
hits a nanoscopic U-shaped gold grating which further twists the beam
in either a right or left-handed direction. This deflects the beam in
many directions and further splits it into its constituent wavelengths
across the color spectrum (image credit: University of Bath, Ventsislav
Valev)

Although
such molecules are built from exactly the same elements they can be
arranged in mirror images of each other, and this configuration
sometimes changes their properties drastically.

Notoriously the morning sickness
drug Thalidomide caused birth defects and deaths in babies before it
was pulled from the market in the 1960s. Investigation showed that the
drug existed in two mirror images - the right-handed form was effective
as a morning sickness drug, but the left-handed form was harmful to
foetuses. This is one example of why testing what 'handedness', or
chirality, a molecule has is essential for many valuable products.

The research team from the Centre
for Photonics and Photonic Materials, and the Centre for Nanoscience
and Nanotechnology at the University of Bath, used a special
white-light laser built in-house and directed it through several
optical components to put a twist on the beam. The twisted laser beam
then hits a nano-scopic U-shaped gold grating which serves as a
template for the light, further twisting the beam in either a right or
left-handed direction. This deflects the beam in many directions and
further splits it into its constituent wavelengths across the colour
spectrum.

By carefully measuring the deflected
light scientists can detect tiny differences in intensity across the
spectrum which inform them about the chirality of the grating the laser
beam interacts with.

The study, published in the journal Advanced Optical Materials, demonstrates the technique as a proof of principle. 61)

Christian Kuppe, the PhD student who
conducted the experiments, said: "At the moment chiral sensing requires
high molecular concentrations because you're looking for tiny
differences in how the light interacts with the target molecule. By
using our gold gratings we aim to use a much smaller amount of
molecules to conduct a very sensitive test of their handedness. The
next step will be to continue to test the technique with a range of
well-known chiral molecules. We hope that this will become a valuable
way to perform really important tests on all sorts of products
including pharmaceuticals and other high-value chemicals."

Dr Ventsislav Valev, who oversaw the
work, said: "There's a great deal of scientific excitement about
miniaturisation and working on nano-sized dimensions at the very small
scale. However, in the rush to go as small as possible, some
opportunities have been overlooked. Working with chiral nano-gratings
is a great example of that."

The information compiled and edited in this article was provided byHerbert
J. Kramer from his documentation of: ”Observation of the Earth
and Its Environment: Survey of Missions and Sensors” (Springer
Verlag) as well as many other sources after the publication of the 4th
edition in 2002. - Comments and corrections to this article are always
welcome for further updates (herb.kramer@gmx.net).